SEC Petition Evaluation Report

Petition SEC-00246

Report Rev. Number: 0

Report Submittal Date: July 3, 2018

Subject Expert(s): Monica Harrison-Maples

Site Expert(s): N/A

Petition Administrative Summary

Petition Under Evaluation

Petition Number: SEC-00246

Petition Type: 83.13

Petition Receipt Date: December 13, 2017

Qualification Date: March 1, 2018

DOE/AWE Facility Name: De Soto Avenue Facility

Petition Class

Petitioner-Requested Class 

Definition:

All workers who worked at the De Soto Avenue Facility in Los Angeles County, 

CA during the period from January 1, 1965 through December 31, 1995.

Class Evaluated by NIOSH: All employees of the Department of Energy, its predecessor agencies, and their 

contractors and subcontractors who worked at the De Soto Avenue Facility in Los 

Angeles County, California, from January 1, 1965 through December 31, 1995.

NIOSH-Proposed Class(es) to be 

Added to the SEC:

None

Related Petition Summary Information

SEC Petition Tracking Number(s): SEC-00093

SEC-00156

SEC-00168

SEC-00234

SEC-00235

Petition Type: 83.13

83.14

83.14

83.14

83.13

DOE/AWE Facility Name: Santa Susana Field Laboratory-Area IV

Area IV of the Santa Susana Field Laboratory

De Soto Avenue Facility

Area IV of the Santa Susana Field Laboratory

Area IV of the Santa Susana Field Laboratory

Petition Status: Class added to the SEC for January 1, 1955 through December 31, 1958

Class added to the SEC for January 1, 1959 through December 31, 1964

Class added to the SEC for January 1, 1959 through December 31, 1964

Class added to the SEC for January 1, 1965 through December 31, 1988

No class added to the SEC
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Related Evaluation Report Information

Report Title: SEC Petition Evaluation Report for Petition SEC-00093

SEC Petition Evaluation Report for Petition SEC-00156

SEC Petition Evaluation Report for Petition SEC-00168

SEC Petition Evaluation Report for Petition SEC-00234

SEC Petition Evaluation Report for Petition SEC-00235

DOE/AWE Facility Name: Santa Susana Field Laboratory-Area IV

Area IV of the Santa Susana Field Laboratory

De Soto Avenue Facility

Area IV of the Santa Susana Field Laboratory

Area IV of the Santa Susana Field Laboratory

ORAU Preparation and Review

ORAU Lead Technical Evaluator: Monica Harrison-Maples

ORAU Peer Review Completed By: Michael Kubiak

DCAS Review and Approval

Peer Review Completed By:

[Signature on File]

Lara Hughes

July 03, 2018

SEC Petition Evaluation Reviewed 

By: [Signature on File]

James W. Neton

July 03, 2018

SEC Petition Evaluation Approved

By: [Signature on File]

Stuart L. Hinnefeld

July 03, 2018
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Evaluation Report Summary: SEC-00246, De Soto Avenue Facility

The National Institute for Occupational Safety and Health (NIOSH) prepared this evaluation report in 

response to a petition to add a class of workers at the De Soto Avenue Facility to the Special Exposure 

Cohort (SEC). The Energy Employees Occupational Illness Compensation Program Act of 2000, as 

amended, (EEOICPA) and 42 C.F.R. pt. 83, Procedures for Designating Classes of Employees as 

Members of the Special Exposure Cohort under the Energy Employees Occupational Illness 

Compensation Program Act of 2000, describe the process for adding new classes to the SEC. 

Petitioner-Requested Class Definition

NIOSH received petition SEC-00246 on December 13, 2017, and qualified it on March 1, 2018. The 

petitioner requested that NIOSH consider the following class: All workers who worked at the De Soto 

Avenue Facility in Los Angeles County, CA during the period from January 1, 1965 through December 

31, 1995. 

Class Evaluated by NIOSH

Based on its preliminary research, NIOSH accepted the petitioner-requested class. NIOSH evaluated 

the following class: All employees of the Department of Energy, its predecessor agencies, and their 

contractors and subcontractors who worked at the De Soto Avenue Facility in Los Angeles County, 

California, from January 1, 1965 through December 31, 1995. 

NIOSH Determination about the Proposed Class(es) to be Added to the SEC

NIOSH has obtained internal monitoring data, including urinalysis sample results for uranium, 

thorium, and gross alpha. NIOSH has in vivo measurements included with the scanned radiological 

exposure files of individual De Soto workers across the radiological operational history of the facility 

through 1995. NIOSH also has external dosimetry results for workers in radiological job assignments. 

NIOSH has developed both an internal dose co-worker model (ORAUT-OTIB-0080) and an external 

dose co-worker model (ORAUT-OTIB-0077) to assess doses to unmonitored De Soto workers. 

NIOSH has reviewed facility plans, procedures, and activity reports to gain an understanding of the 

scope of the potential exposure scenarios during the period under evaluation. Based on its analysis of 

these available resources, NIOSH found no part of the class under evaluation for which it cannot 

estimate radiation doses with sufficient accuracy.

Feasibility of Dose Reconstruction

Per EEOICPA and 42 C.F.R. § 83.13(c) (1), NIOSH has established that it has access to sufficient 

information to: (1) estimate the maximum radiation dose, for every type of cancer for which radiation 

doses are reconstructed, that could have been incurred in plausible circumstances by any member of 

the class; or (2) estimate radiation doses of members of the class more precisely than an estimate of 

the maximum dose. Information available from the site profile and additional resources is sufficient 

to estimate the maximum internal and external potential exposure to members of the evaluated class 

under plausible circumstances during the specified period. 
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The NIOSH dose reconstruction feasibility findings are based on the following: 

• Consistent with previous evaluations, NIOSH finds that it is feasible to reconstruct occupational 

medical dose with sufficient accuracy for De Soto workers for the period from January 1, 1965 

through December 31, 1995, using information and methods in Dose Reconstruction from 

Occupationally Related Diagnostic X-Ray Procedures (ORAUT-OTIB-0006) and the De Soto 

Avenue Facility site profile documents (ORAUT-TKBS-0038-1 through -6). 

• Principal sources of internal radiation for members of the proposed class included exposures to 

radioactive contamination resulting from operations involving unsealed radioactive materials, such 

as nuclear fuel fabrication and radiochemistry operations. Exposures would have been from 

inhalation or ingestion of radionuclides, such as uranium and thorium (including associated 

progeny) during fuel fabrication or laboratory operations associated with research and 

development. 

• NIOSH previously determined in its evaluations of Area IV and De Soto petitions that some 

workers could have received intakes of radioactive materials that went unmonitored. These 

unmonitored exposures are addressed through the internal co-worker intake rates assigned for the 

operation period. 

• Although NIOSH has disqualified in vitro analysis results from vendor Controls for 

Environmental Pollution (CEP) during the period August 1991 through June 1993 for all Santa 

Susana Field Laboratory (SSFL) sites including the De Soto Avenue Facility, NIOSH has 

determined that the lack of CEP in vitro data does not affect NIOSH’s ability to perform 

sufficiently accurate internal dose reconstructions for monitored or unmonitored workers at the 

site. The site performed supplemental whole-body counts that showed no measurable exposures, 

and initiated confirmatory in vitro re-samples analyzed by a new contractor. The in vitro

re-samples confirmed that there were no measurable internal exposures.

• NIOSH has identified thorium campaigns in 1970 and 1979 for which thorium-specific personnel 

and workplace monitoring are available. NIOSH has determined there are sufficient source term, 

process, air monitoring, and pre-work and post-work internal dosimetry data available to bound 

intakes of thorium for the operational period from January 1, 1965 through December 31, 1995 at 

the De Soto Avenue Facility. 

• NIOSH has not identified any data that suggest the possibility for operational americium 

exposures at the De Soto facilities. 

• NIOSH has determined that it is feasible to reconstruct personnel internal exposures with 

sufficient accuracy for employees at the De Soto Avenue Facility for the period from January 1, 

1965 through December 31, 1995. 
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• Principal sources of external radiation for members of the proposed class included exposures to 

photon and beta radiation emitted from research reactor operations, irradiation facility operations, 

and from the various radioactive materials used at the site. To a lesser extent, neutron exposures 

could have resulted from operating the small research reactor and from operations involving 

nuclear fuel. 

• NIOSH has access to photon, beta, and neutron external dosimetry results, as well as other 

supporting data for the entire period under evaluation. NIOSH also has access to area monitoring 

radiation survey summary information. 

• To assess potential external dose to unmonitored employees, NIOSH developed a co-worker dose 

distribution model (ORAUT-OTIB-0077). 

• In its previous SEC evaluations, NIOSH has found, and DHHS has concurred, that it has access to 

sufficient employee monitoring and workplace monitoring data to bound potential external 

exposures for employees at the De Soto Avenue Facility for 1959 through December 31, 1964. 

This current evaluation has found no evidence to the contrary for the period from January 1, 1965 

through December 31, 1995. 

• NIOSH has determined that it is feasible to reconstruct personnel external exposures with 

sufficient accuracy for employees at the De Soto Avenue Facility for the period from January 1, 

1965 through December 31, 1995. 

• Pursuant to 42 C.F.R. § 83.13(c) (1), NIOSH determined that there is sufficient information to 

either: (1) estimate the maximum radiation dose, for every type of cancer for which radiation 

doses are reconstructed, that could have been incurred under plausible circumstances by any 

member of the class; or (2) estimate the radiation doses of members of the class more precisely 

than a maximum dose estimate. 

Health Endangerment Determination

Per EEOICPA and 42 C.F.R. § 83.13(c) (3), a health endangerment determination is not required

because NIOSH has determined that it has sufficient information to estimate dose for the members of 

the evaluated class.
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Table of Contents

Evaluation Report Summary: SEC-00246, De Soto Avenue Facility ..................................................... 3

Table of Contents .................................................................................................................................... 7

1.0 Purpose and Scope ........................................................................................................................ 11

2.0 Introduction .................................................................................................................................. 11

3.0 SEC-00246, De Soto Avenue Facility Class Definitions ............................................................. 12

3.1 Petitioner-Requested Class Definition and Basis ................................................................ 12

3.2 Class Evaluated by NIOSH ................................................................................................. 13

3.3 NIOSH Determination about the Proposed Class(es) to be Added to the SEC ................... 13

4.0 Data Sources Reviewed by NIOSH to Evaluate the Class ........................................................... 14

4.1 Site Profile Technical Basis Documents (TBDs) ................................................................ 14

4.2 ORAU Technical Information Bulletins (OTIBs) and Procedures ..................................... 15

4.3 Facility Employees and Experts .......................................................................................... 16

4.4 Previous Dose Reconstructions ........................................................................................... 16

4.5 NIOSH Site Research Database .......................................................................................... 17

4.6 Other Technical Sources ...................................................................................................... 17

4.7 Documentation and/or Affidavits Provided by Petitioners ................................................. 17

5.0 Radiological Operations Relevant to the Class Evaluated by NIOSH ......................................... 18

5.1 De Soto Avenue Facility Plant and Process Descriptions ................................................... 18

5.2 Radiological Exposure Sources from De Soto Avenue Facility Operations ....................... 21

5.2.1 Internal Radiological Exposure Sources from De Soto Avenue Operations ........... 21

5.2.1.1 Uranium .................................................................................................... 21

5.2.1.2 Americium ................................................................................................ 22

5.2.1.3 Thorium .................................................................................................... 22

5.2.2 External Radiological Exposure Sources from De Soto Avenue Operations .......... 24

6.0 Summary of Available Monitoring Data for the Class Evaluated by NIOSH ............................. 25

6.1 Available De Soto Avenue Facility Internal Monitoring Data ............................................ 25

6.1.1 In Vitro Monitoring ................................................................................................. 26

6.1.2 In Vivo Monitoring .................................................................................................. 28

6.2 Available De Soto Avenue Facility External Monitoring Data ........................................... 29

7.0 Feasibility of Dose Reconstruction for the Class Evaluated by NIOSH ...................................... 29

7.1 Pedigree of De Soto Avenue Facility Data .......................................................................... 30

7.1.1 Internal Monitoring Data Pedigree Review ............................................................. 30

7.1.2 External Monitoring Data Pedigree Review ............................................................ 30

7.2 Evaluation of Bounding Internal Radiation Doses at the De Soto Avenue Facility ........... 31

7.2.1 Evaluation of Bounding Process-Related Internal Doses ........................................ 31

7.2.1.1 Urinalysis Information and Available Data .............................................. 34

7.2.1.2 WBC Measurement Information and Available Data .............................. 35

7.2.1.3 Other Types of Bioassay .......................................................................... 35
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7.2.1.4 Airborne Levels ........................................................................................ 35

7.2.2 Evaluation of Bounding Ambient Environmental Internal Doses ........................... 36

7.2.3 Methods for Bounding Internal Dose at the De Soto Avenue Facility .................... 37

7.2.3.1 Methods for Bounding Operational Period Internal Dose ........................ 37

7.2.3.2 Methods for Bounding Ambient Environmental Internal Dose ............... 38

7.2.4 Internal Dose Reconstruction Feasibility Conclusion ............................................. 39

7.3 Evaluation of Bounding External Radiation Doses at the De Soto Avenue Facility .......... 40

7.3.1 Evaluation of Bounding Process-Related External Doses ....................................... 40

7.3.1.1 Employee Dosimetry Data ....................................................................... 40

7.3.1.2 Area Monitoring Data ............................................................................... 40

7.3.1.3 Alternative Data Sources for Bounding External Dose ............................ 41

7.3.2 Evaluation of Bounding Ambient Environmental External Doses .......................... 41

7.3.3 De Soto Avenue Facility Occupational X-Ray Examinations ................................ 42

7.3.4 Methods for Bounding External Dose at the De Soto Avenue Facility .................. 42

7.3.4.1 Methods for Bounding Operational Period External Dose ....................... 42

7.3.4.2 Methods for Bounding Ambient Environmental External Doses ............. 43

7.3.5 External Dose Reconstruction Feasibility Conclusion ............................................ 43

7.4 Evaluation of Petition Basis for SEC-00246 ....................................................................... 44

7.4.1 Infeasibility of SEC-00234 Area IV Applies to SEC-00246 De Soto ..................... 44

7.4.2 SRE, SNAP, and TRUMP-S ................................................................................... 45

7.4.3 EPA Listed Americium and Thorium as ROCs for De Soto ................................... 46

7.4.4 Incidents .................................................................................................................. 47

7.4.5 SNAP ....................................................................................................................... 47

7.5 Other Potential SEC Petition Issues Identified During the Evaluation ............................... 48

7.5.1 Thorium-Grinding Operation .................................................................................. 48

7.5.2 Controls for Environmental Pollution (CEP) .......................................................... 49

7.6 Summary of Feasibility Findings for Petition SEC-00246 .................................................. 50

8.0 Evaluation of Health Endangerment for Petition SEC-00246 ...................................................... 51

9.0 Class Conclusion for Petition SEC-00246 ................................................................................... 51

10.0 References .................................................................................................................................... 53

Attachment One: Data Capture Synopsis .............................................................................................. 59
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Tables

Table 4-1: No. of De Soto Avenue Facility Claims Submitted Under the Dose Reconstruction Rule . 16

Table 7-1: Summary of Feasibility Findings for SEC-00246 ............................................................... 50

Table A1-1: Summary of Holdings in the SRDB for De Soto Avenue Facility ................................... 59

Table A1-2: Database Searches for De Soto Avenue Facility .............................................................. 65

Figures

Figure 5-1: Footprint of the De Soto Avenue Facility .......................................................................... 20
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SEC Petition Evaluation Report for SEC-00246

ATTRIBUTION AND ANNOTATION: This is a single-author document. All conclusions drawn from 

the data presented in this evaluation were made by the ORAU Team Lead Technical Evaluator: M. 

Harrison-Maples, Oak Ridge Associated Universities. The rationales for all conclusions in this 

document are explained in the associated text.

1.0 Purpose and Scope

This report evaluates the feasibility of reconstructing radiation doses for all employees of the 

Department of Energy, its predecessor agencies, and their contractors and subcontractors who worked at 

the De Soto Avenue Facility in Los Angeles County, California, from January 1, 1965 through December 

31, 1995. It provides information and analyses germane to considering a petition for adding a class of 

employees to the congressionally-created SEC. 

This report does not make any determinations concerning the feasibility of dose reconstruction that 

necessarily apply to any individual energy employee who might require a dose reconstruction from 

NIOSH. This report also does not contain the final determination as to whether the proposed class 

will be added to the SEC (see Section 2.0). 

This evaluation was conducted in accordance with the requirements of EEOICPA, 42 C.F.R. pt. 83, 

and the guidance contained in the Division of Compensation Analysis and Support’s (DCAS) Internal 

Procedures for the Evaluation of Special Exposure Cohort Petitions, DCAS-PR-004.1

1 DCAS was formerly known as the Office of Compensation Analysis and Support (OCAS).

2.0 Introduction

Both EEOICPA and 42 C.F.R. pt. 83 require NIOSH to evaluate qualified petitions requesting that the 

Department of Health and Human Services (DHHS) add a class of employees to the SEC. The 

evaluation is intended to provide a fair, science-based determination of whether it is feasible to 

estimate with sufficient accuracy the radiation doses of the class of employees through NIOSH dose 

reconstructions.2

2 NIOSH dose reconstructions under EEOICPA are performed using the methods promulgated under 42 C.F.R. pt. 82 and 

the detailed implementation guidelines available on the NIOSH Radiation Dose Reconstruction Program webpage. 

42 C.F.R. § 83.13(c)(1) states: Radiation doses can be estimated with sufficient accuracy if NIOSH 

has established that it has access to sufficient information to estimate the maximum radiation dose, 

for every type of cancer for which radiation doses are reconstructed, that could have been incurred in 

plausible circumstances by any member of the class, or if NIOSH has established that it has access to 

sufficient information to estimate the radiation doses of members of the class more precisely than an 

estimate of the maximum radiation dose.

Under 42 C.F.R. § 83.13(c)(3), if it is not feasible to estimate with sufficient accuracy radiation doses 

for members of the class, then NIOSH must determine that there is a reasonable likelihood that such 

 
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radiation doses may have endangered the health of members of the class. The regulation requires 

NIOSH to assume that any duration of unprotected exposure may have endangered the health of 

members of a class when it has been established that the class may have been exposed to radiation 

during a discrete incident likely to have involved levels of exposure similarly high to those occurring 

during nuclear criticality incidents. If the occurrence of such an exceptionally high-level exposure has 

not been established, then NIOSH is required to specify that health was endangered for those 

employees who were employed for at least 250 aggregated work days within the parameters 

established for the class or in combination with work days within the parameters established for one 

or more other SEC classes. 

NIOSH is required to document its evaluation in a report, and to do so, relies upon both its own dose 

reconstruction expertise as well as technical support from its contractor, Oak Ridge Associated 

Universities (ORAU). Once completed, NIOSH provides the report to both the petitioner(s) and the 

Advisory Board on Radiation and Worker Health (Advisory Board). The Advisory Board will 

consider the NIOSH evaluation report, together with the petition, petitioner(s) comments, and other 

information the Advisory Board considers appropriate, in order to make recommendations to the 

Secretary of DHHS on whether or not to add one or more classes of employees to the SEC. Once 

NIOSH has received and considered the advice of the Advisory Board, the Director of NIOSH will 

propose a decision on behalf of DHHS. The Secretary of DHHS will make the final decision, taking 

into account the NIOSH evaluation, the advice of the Advisory Board, and the proposed decision 

issued by NIOSH. As part of this decision process, petitioners may seek a review of certain types of 

final decisions issued by the Secretary of DHHS.

3

3 See 42 C.F.R. pt. 83 for a full description of the procedures summarized here. Additional internal procedures are 

available on the NIOSH Radiation Dose Reconstruction Program webpage.

3.0 SEC-00246, De Soto Avenue Facility Class Definitions

The following subsections address the evolution of the class definition for SEC-00246, De Soto 

Avenue Facility. When a petition is submitted, the requested-class definition is reviewed as 

submitted. Based on its review of the available site information and data, NIOSH will make a

determination whether to qualify for full evaluation all, some, or no part of the petitioner-requested

class. If some portion of the petitioner-requested class is qualified, NIOSH will specify that class 

along with a justification for any modification of the petitioner’s class. After a full evaluation of the 

qualified class, NIOSH will determine whether to propose a class for addition to the SEC and will 

specify that proposed class definition. 

3.1 Petitioner-Requested Class Definition and Basis

NIOSH received petition SEC-00246 on December 13, 2017. The petitioner requested that NIOSH 

consider the following class: All workers who worked at the De Soto Avenue Facility in Los Angeles 

County, CA during the period from January 1, 1965 through December 31, 1995. 

The petitioner provided information and affidavit statements in support of the petitioner’s belief that 

accurate dose reconstruction over time is impossible for the De Soto employees in question. NIOSH 

deemed the following information and statements sufficient to qualify SEC-00246 for evaluation: 

 
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• The petitioner provided statements asserting that the operations conducted at the De Soto 

Avenue Facility: (1) involved contractors and subcontractors shared with Area IV of the 

SSFL; and (2) involved the same hazards for which NIOSH determined it was unable to 

reconstruct radiation dose with sufficient accuracy for Area IV (i.e., occupational exposure 

to americium and thorium and its associated progeny) from January 1, 1965 through 

December 31, 1988. 

• The petition included documentation describing thorium operations, including selections 

from log books and incident reports intended to document the use of americium and 

thorium “well into the Site Remediation period.” The petition also provided citations of 

licensing documents authorizing the storage and use of special nuclear materials, including 

americium and thorium. 

Based on its De Soto Avenue Facility research and data capture efforts, NIOSH determined that it has 

access to bioassay data, external monitoring records, radiological monitoring methods and procedures, 

environmental monitoring reports, and facility characterization records for De Soto Avenue Facility 

employees during the period under evaluation. However, NIOSH also determined that potential 

americium and thorium source term, monitoring data, and exposure scenarios at De Soto Avenue had 

not been fully evaluated. NIOSH concluded that there is sufficient documentation to support that 

thorium work was conducted at the De Soto Avenue Facility, for at least part of the petitionerrequested time period. While there is evidence that the facility did monitor for thorium in special 

circumstances; NIOSH determined the extent of that monitoring and the effectiveness of documenting 

worker exposure to thorium warranted further evaluation. The information and statements provided 

by the petitioner qualified the petition for further consideration by NIOSH, the Advisory Board, and 

DHHS. The petition qualified for full evaluation on March 1, 2018. The details of the petition basis 

are addressed in Section 7.4. 

3.2 Class Evaluated by NIOSH

Based on its preliminary research, NIOSH accepted the petitioner-requested class because of the need 

to further evaluate the availability of dosimetry and related information for estimating radiation doses 

due to thorium and americium exposures at the facility. NIOSH also noted that Controls for 

Environmental Pollution (CEP) was the primary vendor for bioassay sample analyses from August 

1991 through June 1993. Bioassay analyses performed by CEP are disqualified from consideration of 

dose by NIOSH due to concerns with the vendor’s product quality. In 2016, the involvement of CEP 

qualified the Area IV petition SEC-00235 for evaluation, and NIOSH found that the exclusion of CEP 

data had no impact on dose reconstruction feasibility. Because the Area IV and De Soto facilities 

used the same dosimetry programs, NIOSH determined it was also appropriate to assess the 

disqualification of CEP-provided bioassay results on De Soto dose reconstruction feasibility. 

Therefore, NIOSH defined the following class for further evaluation: All employees of the 

Department of Energy, its predecessor agencies, and their contractors and subcontractors who worked 

at the De Soto Avenue Facility in Los Angeles County, California, from January 1, 1965 through 

December 31, 1995.

3.3 NIOSH Determination about the Proposed Class(es) to be Added to the SEC

NIOSH has obtained internal monitoring data, including urinalysis sample results for uranium, 

thorium, and gross alpha. NIOSH has in vivo measurements included with the scanned radiological 
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exposure files of individual De Soto workers across the radiological operational history of the facility 

through 1995. NIOSH also has external dosimetry results for workers in radiological job assignments. 

NIOSH has developed both an internal dose co-worker model (ORAUT-OTIB-0080) and an external 

dose co-worker model (ORAUT-OTIB-0077) to assess doses to unmonitored De Soto workers. 

NIOSH has reviewed facility plans, procedures, and activity reports to gain an understanding of the 

scope of the potential exposure scenarios during the period under evaluation. Based on its analysis of 

these available resources, NIOSH found no part of the class under evaluation for which it cannot 

estimate radiation doses with sufficient accuracy.

4.0 Data Sources Reviewed by NIOSH to Evaluate the Class

As is standard practice, NIOSH completed an extensive database and Internet search for information 

regarding the De Soto Avenue Facility. The database search included the DOE Legacy Management 

Considered Sites database, the DOE Office of Scientific and Technical Information (OSTI) SciTech 

Connect database, and the Hanford Declassified Document Retrieval System. In addition to general 

Internet searches, the NIOSH Internet search included OSTI OpenNet Advanced searches, the Nuclear 

Regulatory Commission (NRC) Agency-wide Documents Access and Management (ADAMS) web 

searches, and the DOE-National Nuclear Security Administration-Nevada Site Office-search. 

Attachment One includes a summary of De Soto Avenue Facility-related documents. The summary 

specifically includes data capture details and general descriptions of the documents retrieved.

In addition to the database and Internet searches listed above, NIOSH identified and reviewed 

numerous data sources to determine information relevant to determining the feasibility of dose 

reconstruction for the class of employees under evaluation. This included determining the availability 

of information on personal monitoring, area monitoring, industrial processes, and radiation source 

materials. The following subsections summarize the data sources identified and reviewed by NIOSH. 

4.1 Site Profile Technical Basis Documents (TBDs)

A Site Profile provides specific information concerning the documentation of historical practices 

documented at the specified site. Dose reconstructors can use the Site Profile to evaluate internal and 

external dosimetry data for monitored and unmonitored employees, and to supplement, or substitute 

for, individual monitoring data. A Site Profile consists of an Introduction and five Technical Basis 

Documents (TBDs) that provide process history information, information on personal and area 

monitoring, radiation source descriptions, and references to primary documents relevant to the 

radiological operations at the site. The Site Profile for a small site may consist of a single document. 

As part of NIOSH’s evaluation detailed herein, it examined the following TBDs for insights into De 

Soto Avenue Facility operations or related topics/operations at other sites: 

• TBD for Atomics International – Introduction, ORAUT-TKBS-0038-1; Rev. 01; August 30, 2006; 

SRDB Ref ID: 30080 

• TBD for Energy Technology Engineering Center – Site Description, ORAUT-TKBS-0038-2; Rev. 

00; February 2, 2006; SRDB Ref ID: 22140 

• TBD for the Area IV of the Santa Susana Field Laboratory, the Canoga Avenue Facility (Vanowen 

Building), the Downey Facility, and the De Soto Avenue Facility (Sometimes Referred to as 
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Energy Technology Engineering Ctr. [ETEC] or Atomics Int.) – Occupational Medical Dose, 

ORAUT-TKBS-0038-3; Rev. 02; October 31, 2008; SRDB Ref ID: 53184 

• TBD for the Area IV of the Santa Susana Field Laboratory, the Canoga Avenue Facility (Vanowen 

Building), the Downey Facility, and the De Soto Avenue Facility (Sometimes Referred to as 

Energy Technology Engineering Ctr. [ETEC] or Atomics International) – Occupational 

Environmental Dose, ORAUT-TKBS-0038-4; Rev. 02; April 26, 2010; SRDB Ref ID: 80536 

• TBD for the Area IV of the Santa Susana Field Laboratory, the Canoga Avenue Facility (Vanowen 

Building), the Downey Facility, and the De Soto Avenue Facility (Sometimes Referred to as 

Energy Technology Engineering Ctr. [ETEC] or Atomics International)– Occupational Internal 

Dose, ORAUT-TKBS-0038-5; Rev. 01; April 26, 2010; SRDB Ref ID: 80541 

• TBD for the Area IV of the Santa Susana Field Laboratory, the Canoga Avenue Facility (Vanowen 

Building), the Downey Facility, and the De Soto Avenue Facility (Sometimes Referred to as 

Energy Technology Engineering Ctr. [ETEC] or Atomics International)– Occupational External 

Dose, ORAUT-TKBS-0038-6; Rev. 02; April 26, 2010; SRDB Ref ID: 80538 

4.2 ORAU Technical Information Bulletins (OTIBs) and Procedures

An ORAU Technical Information Bulletin (OTIB) is a general working document that provides 

guidance for preparing dose reconstructions at particular sites or categories of sites. An ORAU 

Procedure provides specific requirements and guidance regarding EEOICPA project-level activities, 

including preparation of dose reconstructions at particular sites or categories of sites. NIOSH 

reviewed the following OTIBs and procedure as part of its evaluation: 

• OTIB: Dose Reconstruction from Occupationally Related Diagnostic X-Ray Procedures, ORAUTOTIB-0006, Rev. 04; effective June 20, 2011; SRDB Ref ID: 98147

• OTIB: Analysis of Coworker Bioassay Data for Internal Dose Assignment, ORAUT-OTIB-0019, 

Rev. 01; effective October 7, 2005; SRDB Ref ID: 19438

• OTIB: Dose Reconstruction During Residual Radioactivity Periods at Atomic Weapons Employer 

Facilities, ORAUT-OTIB-0070; effective March 5, 2012; SRDB Ref ID: 108851

• OTIB: External Coworker Dosimetry Data for Area IV of the Santa Susana Field Laboratory, the 

Canoga Avenue Facility (Vanowen Building), and the De Soto Avenue Facility (sometimes 

referred to as Energy Technology Engineering Center [ETEC] or Atomics International), 

ORAUT-OTIB-0077, Rev. 00; effective August 3, 2009; SRDB Ref ID: 72162

• OTIB: Guidance on Assigning Occupational X-Ray Dose Under EEOICPA for X-Rays 

Administered Off Site, ORAUT-OTIB-0079, Rev. 02; effective June 15, 2017; SRDB Ref ID: 

166967

• OTIB: Internal Coworker Dosimetry Data for Area IV of the Santa Susana Field Laboratory and 

the De Soto Avenue Facility, ORAUT-OTIB-0080, Rev. 00; effective March 14, 2014; SRDB Ref 

ID: 131215
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• Procedure: Generating Summary Statistics for Coworker Bioassay Data, ORAUT-PROC-0095, 

Rev. 00; effective June 5, 2006; SRDB Ref ID: 73397

4.3 Facility Employees and Experts

To obtain additional information, NIOSH interviewed two former workers, one employed at both 

Area IV (2017) and De Soto Avenue (2018a), and the other employed at De Soto (2018b). 

• Personal Communication, 2017, Personal Communication with Area IV - Santa Susana Field 

Laboratory Health and Safety Employee; Telephone Interview by ORAU Team and NIOSH; April 

18, 2017; SRDB Ref ID: 166532

• Personal Communication, 2018a, Personal Communication with Former De Soto Avenue Facility 

Engineering Employee; Telephone Interview by ORAU Team, NIOSH, and Boeing Company; 

May 1, 2018; SRDB Ref ID: 172299

• Personal Communication, 2018b, Personal Communication with Former De Soto Avenue Facility 

Health and Safety Employee; Telephone Interview by ORAU Team, NIOSH, and Boeing 

Company; May 16, 2018; SRDB Ref ID: 172300

4.4 Previous Dose Reconstructions

NIOSH reviewed its NIOSH DCAS Claims Tracking System (referred to as NOCTS) to locate

EEOICPA-related dose reconstructions that might provide information relevant to the petition 

evaluation. Table 4-1 summarizes the results of this review. (NOCTS data available as of May 21, 

2018) 

Table 4-1: No. of De Soto Avenue Facility Claims Submitted Under the Dose Reconstruction Rule

Description Totals

Total number of claims submitted for dose reconstruction 292

Total number of claims submitted for energy employees who worked during the period under 

evaluation (January 1, 1965 through December 31, 1995) 255

Total number of claims submitted for energy employees who started their employment during the 

period under evaluation (January 1, 1965 through December 31, 1995) 210

Number of dose reconstructions completed for energy employees who worked during the period

under evaluation (i.e., the number of such claims completed by NIOSH and submitted to the 

Department of Labor for final approval)

215

Number of claims for which internal dosimetry records were obtained for the time period in the 

evaluated class definition 64

Number of claims for which external dosimetry records were obtained for the time period in the 

evaluated class definition 104

NIOSH reviewed each claim to determine whether internal and/or external personal monitoring 

records could be obtained for the employee. In addition to exposure data received from DOE in 

response to requests for individual claimant history data, NIOSH has scans created in 2009 of 
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employee radiological exposure files. The NIOSH scans included radiological exposure files through 

2001. A sampling of DOE-supplied claimant data found sample results matching those in the scanned 

employee radiological exposure files. Internal dosimetry results in both the DOE claimant-response 

files and the scans include urine bioassay, fecal bioassay, thyroid measurement, chest scan, total body 

count, and some post-incident wound and nasal swab counting results. Results used to assess external 

exposure, including deep, shallow, extremity, eye, and neutron results (indicated as thermal or fast), 

are found in both the 2009 scanned files and the DOE claimant-response files. 

4.5 NIOSH Site Research Database

NIOSH also examined its Site Research Database (SRDB) to locate documents supporting the 

assessment of the evaluated class. Of the 3,143 documents in the SRDB that are related to the De 

Soto Avenue Facility, Atomics International, and Area IV of the SSFL, 588 pertain solely to the De 

Soto Avenue Facility. These documents were evaluated for their relevance to this petition. The 

documents include historical background on radiological work plans and procedures, occupational 

dosimetry information including bioassay data, exposure investigations, radiological incidents, 

radioactive material licenses and use authorizations, site environmental and work area radiation 

surveys, air monitoring data, documentation of radiological work permits, radiological restricted 

access area entry permits and decommissioning documentation. 

4.6 Other Technical Sources

In qualifying and evaluating the petition, NIOSH reviewed the following report: 

REPORT: Analysis of Stratified Coworker Datasets, ORAUT-RPRT-0053, Rev. 02; effective 

October 8, 2014; SRDB Ref ID: 136245 

4.7 Documentation and/or Affidavits Provided by Petitioners

In qualifying and evaluating the petition, NIOSH reviewed the following documents submitted by the 

petitioners:

• Special Exposure Cohort Petition—Form B, with attachments; received December 13, 2017; DSA 

Ref ID: 128711

• Petitioner Response & Clarifications to Summary of Telephone Conversation and Agreements 

SEC-00246 DeSoto Facility 1965-1995; [name redacted], CORE Advocacy for Nuclear & 

Aerospace Workers; received February 12, 2018; DSA Ref ID: 128791

• Information about Visitor Logs in the De Soto Facility Log Book, submitted as an email to NIOSH 

staff; received February 27, 2018; DSA Ref ID: 128837

• Missing In Vivo, Whole-Body Count Scans, handwritten notes memo; received March 30, 2018; 

DSA Ref ID 128857
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5.0 Radiological Operations Relevant to the Class Evaluated by 

NIOSH

The following subsections summarize both radiological operations at the De Soto Avenue Facility 

from January 1, 1965 through December 31, 1995 and the information available to NIOSH to 

characterize particular processes and radioactive source materials. From available sources NIOSH has 

gathered process and source descriptions, information regarding the identity and quantities of each 

radionuclide of concern, and information describing processes through which radiation exposures may 

have occurred and the physical environment in which they may have occurred. The information 

included within this evaluation report is intended only to be a summary of the available information. 

5.1 De Soto Avenue Facility Plant and Process Descriptions 

The De Soto Avenue Facility site is located in Canoga Park, CA, and performed light industrial work 

with some laboratory-scale research and development. The facility was constructed in 1959 and was 

originally the headquarters of Atomics International. The radiological activities from the Canoga 

Avenue Facility were transferred to the De Soto Avenue Facility. Atomic Energy Commission (AEC) 

or Department of Energy (DOE) work conducted at De Soto Avenue included engineering design, 

construction, and nuclear fuel fabrication. Radiological operations at the De Soto Avenue Facility 

included: fuel fabrication operations in Building 001, operation of the L-77 low-power research 

reactor, radiochemistry support, operation of the Gamma Irradiation Facility (GIF) (an above-ground 

vault using sealed Cs-137 and Co-60 sources for radiation-hardening tests of electronic components 

and for food-irradiation research), and operation of the Mass Spectroscopy Laboratory (Mass Spec 

Lab) (which analyzed radioactive samples for helium content) in Building 004. The Mass Spec Lab 

historically was also known as the Helium Laboratory. 

Radiological operations were conducted using nuclear fuel material and other radioactive materials in 

Buildings 001 and 0044

4 Buildings 001 and 004 were renumbered 101 and 104 in 1984. Much of the historical documentation refers to the 

original building numbers. For consistency, this report uses 001 and 004 throughout.

 from 1959 through 1983 (see Figure 5-1). All nuclear activities except 

operation of the GIF and some applied physics studies were terminated in 1983. All the building 

radiological work areas, except the GIF and the small area devoted to the applied physics activities, 

were decontaminated and released for unrestricted use in 1984. From 1983 through 1995, radiological 

work continued in Building 004 at a reduced level. Irradiation operations in the GIF (Bldg. 104) were 

terminated in 1994, and radiation sources were shipped offsite. Research studies in applied physics 

and physical chemistry using activated materials in the Mass Spec Lab were terminated in May 1995 

(De Soto Site, undated) and the lab was relocated to a DOE facility at Battelle-Pacific Northwest 

National Lab in early 1996. 

The Mass Spec Lab included: Rooms 414-69, 416-72, 414-75, 416-76, 416-76A, 414-77, 416-80, 

416-80A and 414-81 in the northeast section of the 1st floor of Building 004. It was operational for 

approximately 25 years and was one of the original facilities in the world that performed helium 

analyses on activated materials. The Mass Spec Lab analyzed low-level, activated test samples for 

universities and national laboratories. The laboratory housed a Helium Mass Spectroscopic Analyzer 

 
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capable of measuring irradiated metal samples for He-3/H-4 ratios useful in the evaluation of steels 

for use in reactor cores. Typical isotopes controlled by the laboratory were mainly activation 

products, such as Mn-54, Mn-56, Co-58, Co-60, Fe-59, and Nb-95. The laboratory also operated a 

mass spectrograph for the measurement of heavy elements, primarily isotopes of uranium, used in fuel 

fabrication. Low-level radioactive materials were also stored in the Mass Spec Lab until operations 

ceased (Lupo, 1999). 

The Space Nuclear Auxiliary Power (SNAP) program was begun in 1955 and terminated in 1973 (see 

Table 5-1). Atomics International (AI) did development work for the U.S. government on a series of 

compact light-weight, reliable nuclear reactors capable of producing from 500 W up to 1000 kWe as 

part of the SNAP program. The SNAP-8 Experimental Reactor (S8ER) and SNAP-8 Developmental 

Reactor (S8DR) were designed and operated by Atomics International under contract with NASA, 

were tested and inspected during the 1960s, and used highly-enriched uranium-zirconium hydride fuel 

with Hastelloy N cladding, as did the SNAP-10A reactors (SNAP Reactor Overview, 1984). The 

S8ER, S8DR, and SNAP 10A reactors were designed, assembled, and tested during the period under 

evaluation. The program was very large; most of the fuel fabrication and assembly of individual new 

components was performed at the De Soto facility. All development, system assembly, checkout, and 

qualification was performed at Area IV (ETEC, 1991). After testing, the reactors underwent 

assessment of the stresses on reactor structures (e.g., fuel, cladding), also at Area IV. De Soto 

operations did not include handling or inspection of systems following reactor testing, or exposure to 

the irradiated fuel or SNAP reactor materials or structures.

Table 5-1: Space Nuclear Auxiliary Power (SNAP) Reactors Designed at De Soto

Operational Details S8ER SNAP 10A

Flight System 3

SNAP 10A

Flight System 4 S8DR

Critical May 1963 January 1965 April 1965 June 1968

Shutdown April 1965 March 1966 May 1965 December 1969

Thermal power 600 kWt 38 kWt 43 kWt 600/1000 kWt

Time at Power and 

Temperature

1 year at 704 C, 

400-600 kWt

417 days 43 days 7500 hours

Note: The above reactors were assembled and tested at Area IV.

Buildings 001 and 004 have been decommissioned and decontaminated (D&D). D&D included: 

removal of all fuel and radioactive materials and waste; removal of contaminated equipment, drain 

lines, tanks, and ventilation ducts; and cleaning of all surfaces, including floors, walls and ceilings.

For the period under evaluation, the De Soto Avenue Facility radiological workforce consisted of 

approximately 100 to 200 employees at any given time (Personal Communication, 2018b). 
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Figure 5-1: Footprint of the De Soto Avenue Facility 

Source: De Soto Survey, 1985
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5.2 Radiological Exposure Sources from De Soto Avenue Facility Operations

The following subsections provide an overview of the internal and external exposure sources for the 

De Soto Avenue Facility class under evaluation.

5.2.1 Internal Radiological Exposure Sources from De Soto Avenue Operations

This section addresses potential internal exposures to radionuclides at the De Soto Avenue Facility 

during the period under evaluation (1965 through 1995). The primary potential sources of internal 

radiation exposure at the site were inhalation and ingestion of radioactive contamination that could 

have resulted from operations involving unsealed radioactive materials, such as nuclear fuel 

fabrication and radiochemistry operations. 

The De Soto Avenue Facility, as part of the SSFL complex, was supported by a full-time technical 

staff of radiation and nuclear safety specialists. These staff were responsible for determining and 

implementing specific safety techniques, radiation monitoring, dosimetry, and environmental 

monitoring programs. This same staff supported the Area IV operations under the same procedures 

and administrative guidance. The centralized nature of the radiological monitoring program resulted 

in the data for the associated sites being combined in centralized record systems. These same data 

were used to develop NIOSH’s internal co-worker dose reconstruction methodology. The monitoring 

data from these programs have been previously assessed to ascertain their value for determining dose 

reconstruction feasibility during the evaluations for SEC-00093 Area IV, SEC-00156 Area IV, SEC00168 De Soto, SEC-00234 Area IV, and SEC-00235 Area IV. 

The engineering and design work performed at De Soto Avenue was implemented and tested at SSFL 

Area IV. The two facilities collaborated on the same project goals; however, they had different 

contributions. Area IV was primarily a nuclear development and testing facility, conducting reactor 

and critical testing operations with support operations, including all the functions carried out at De 

Soto Avenue and more. Similar to De Soto Avenue, Area IV operations included nuclear fuel 

manufacturing, fuel storage, and source fabrication. Area IV fabricated reactor fuel that included 

uranium, plutonium and, in the cases of the Sodium Reactor Experiment (SRE) and Advanced 

Epithermal Thorium Reactor (AETR), thorium. Although plutonium fuel was manufactured at Area 

IV, according to operational descriptions, none of the reactors or criticality experiments operated at 

Area IV used plutonium as a fuel (Rucker, 2009). These fuel materials and their progeny created 

exposure potentials at Area IV that did not occur at De Soto Avenue. Unlike De Soto Avenue, Area 

IV performed disassembly and examination of reactors and used reactor fuel assemblies, and 

conducted research on reprocessing used reactor fuel, which could have involved exposures to 

transuranic (TRU) materials. NIOSH has found no indication of any TRU-material sources of 

exposure at De Soto Avenue. 

This section of the report concentrates on the assessment of uranium exposures, and potential 

americium and thorium exposures (for which this petition qualified for evaluation). 

5.2.1.1 Uranium 

De Soto Avenue focused on fuel-element fabrication (using uranium) and applied research. Uranium 

comprised the bulk of the radiological material on site. NRC-licensed fuel-fabrication operations for 

the Advanced Test Reactor (ATR) were conducted in Building 001 from 1966 to 1968. Briquettes of 

a 93% enriched uranium and aluminum alloy known as uranium aluminide (UAlx) were formed in an 
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electric arc-melting furnace. These briquettes were crushed to form a powder, which was 

cold-pressed into compacts that became the cores of the fabricated fuel plates. These operations were 

performed within containment and with air sampling. The room where these activities took place was 

known as the “powder room.” Radiochemistry support operations involving hot chemistry 

laboratories, an emission spectroscopy laboratory, and an X-ray diffraction laboratory were conducted 

on the first and second floors of Building 004. Some of the uranium-aluminum alloy development 

work occurred in sealed gloveboxes. Fuel manufacturing of all types ended in 1983 (ORAUT-TKBS0038-5, Attachment H). 

5.2.1.2 Americium

Research of facility records and interviews with former workers revealed limited storage of americium 

sealed sources and research material at the De Soto site (Personal Communication, 2018a; Personal 

Communication, 2018b). The site maintained discrete sources of americium, specifically for 

instrumentation/equipment (i.e., a 10 mCi sealed source of Am-241 for an IPL Model GFS or 

Amersham Model AMPC.2) and held NRC or State of California licenses for them (License, 1981-

1991). Americium sources were also on site in commercial items, such as smoke detectors and 

possibly in radiographic equipment (SSFL Operations, 1989). The De Soto site also conducted some 

research licensed by the State of California using radioactive materials containing approximately 30 

kCi of Co-60 and 560 kCi of Cs-137. This research was conducted in Building 004, in the Applied 

Nuclear Technology Laboratories, and in the Gamma Irradiation Facility (Monitoring Report, 1989).

The Transuranic Management by Pyropartitioning-Separation (TRUMP-S) program used research 

amounts of plutonium, neptunium, and americium radioisotopes associated with the disposal of spent 

nuclear fuel in order to develop fundamental thermodynamic and electrochemical data on various 

transuranic materials so that processes could be developed for separating and destroying long-lived 

radioactive isotopes from spent nuclear fuel. These long-lived radioactive isotopes could then be 

destroyed by fissioning them in a nuclear reactor or accelerator, thereby eliminating the long-term 

hazard (Rucker, 2009). In 1989, TRUMP-S radiological materials, including 75 g of depleted 

uranium, 5 g of plutonium, 4 g of neptunium, and 4 g of americium were received at De Soto (Rucker, 

2009). Review of the documentation referencing the TRUMP-S program indicates that the program 

never operated at the De Soto Avenue Facility. The materials were transferred to the Fuel Storage 

Facility at Area IV (Building 4064) for use in TRUMP-S testing that was planned for the Hot Lab 

(Area IV, Building 4020). The program was transferred from Area IV to the University of Missouri 

sometime after 1990; the materials were stored in Building 4064 until shipment. The program never 

operated at Area IV.

5.2.1.3 Thorium 

NIOSH has identified detailed documentation of thorium work episodes in 1970 and 1979, providing 

source term, operational procedures, radiological protection protocols, names of individual operators, 

and dates of work. The documentation of the work dates and individuals involved corresponds with 

the available thorium bioassay results for the site. No other thorium work campaigns were verified 

during the literature research or by interviews with former De Soto workers. NIOSH has determined 

that these operations in 1970 and 1979 represent the potential exposure scenarios associated with 

bounding thorium internal exposures during the De Soto operational period from January 1, 1965 

through December 31, 1995. 
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A May 1970 document, Authorization [No. 13] for Use of Radioactive Materials or Radiation 

Producing Devices documents the approval of a fabrication operation involving ThO2 powder 

containing 5 kg of natural thorium (Authorization, May1970). The purpose was to fabricate 

fuel-simulant discs to be used in space-flight-related transit capsule testing. Three different processes 

were investigated and documented to attain the required product quality: Cold Press and Sinter, Hot 

Press, and Explosive Forming. Most of the work was to be done in the SNAP area in Building 001. 

Powder work was to be done in a glove box under negative pressure. 

A June 1970 document, Authorization [No. 21] for Use of Radioactive Materials or Radiation 

Producing Devices, documents the post-test analyses for the transit capsule testing (Authorization, 

Jun1970). The transit capsules underwent impact, fragmentation, overpressure, and fire testing at 

Sandia Laboratories and then were shipped to Atomics International for post-test evaluation. The 

process of receiving the capsules at De Soto, a description of the facilities used, and the detailed 

process of disassembling and assessing the capsules is documented. The post-test analyses were to be 

conducted in Building 001. An internal letter (Harris, 1970) describes the disassembly work in the 

De Soto Avenue Hot Shop (Building 004) as occurring during June-July 1970, with the following 

estimates of hours from June 15 through July 30, by department: 

• Hot Shop (Dept. 789): 160 hours 

• Health and Safety (Dept. 779): 36 hours 

• Photographic Services (Dept. 055): 76 hours 

• Inspection (Dept. 754): 100 hours 

• QA (Dept. 755): 20 hours 

• Chemistry (Dept. 741): 150 hours 

• Metallography (Dept. 737): 150 hours 

• Vault (Dept. 785): 20 hours 

• Radioisotope Materials Development (Dept. 737): 100 hours 

NIOSH has identified a second major thorium operation at the De Soto Avenue facility. NIOSH has 

access to documentation regarding a Rockwell Isotopes Committee review of a proposal to machine 

thorium at De Soto in 1979 (Tuttle, 1979; Begley, 1979). The job was grinding corners off 

approximately 540 plates of thorium metal. The thorium material was 19 years post-fabrication, and 

thus, essentially in equilibrium. These documents specify the work procedures at a very detailed level 

(Health and Safety, 1979) to include: the amount of source term (approximately 200 kg of thorium 

metal); how much was expected to be removed (150 g); Health and Safety precautions; worker 

personal protective equipment (PPE); work location (Room 115-37 of Building 001); air sampling 

data, including a log of personal lapel air sampling and results for an air sampler attached to the 

grinding wheel; restricted access area entry permit, and identities of the workers. The daily log

maintained for this operation documents activity from February 28, 1979 through March 12, 1979 

(Grinding Log, 1979).

Information available to NIOSH indicates that the De Soto thorium work, both in oxide and metallic 

form, was limited, distinct, and well-documented. The same individuals are associated with both the 

oxide and metallic work. The site took appropriate precautions and worked to limit exposure during 
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thorium operations. NIOSH has access to bioassay data, breathing zone air data, and source-term 

information contained in detailed work documentation for thorium operations at De Soto Avenue. 

These data are available for developing bounding thorium intake rates. 

5.2.2 External Radiological Exposure Sources from De Soto Avenue Operations

The potential for external radiation dose existed at the De Soto Avenue Facility in all areas where 

radioactive materials were handled or stored. Based on the site operations, sources of exposure 

included photon and beta radiation emitted from the various radioactive materials used at the site. To 

a lesser extent, neutron exposures could have resulted from operating the small research reactor and 

from operations involving nuclear fuel. 

The primary potential sources of external dose for De Soto Avenue Facility employees during the 

period under evaluation (1965 through 1995) were surface contamination in the nuclear fuel 

fabrication areas of Building 001, and in the radiochemistry support operations areas of Building 004, 

as well as direct exposure to irradiation sources in use in the facility. 

Only uranium-bearing fuels with enrichments in U-235 ranging from normal uranium to 

highly-enriched were processed in Building 001. Typical fuel forms included uranium metal, alloys 

of uranium-molybdenum, uranium-aluminum, uranium-zirconium, and uranium with rare earths. All 

materials were solids except for the uranyl sulphate fuel for the L-77 reactor; no processing activities 

were conducted on any liquid fuels (Nuclear Activities, 1991). The uranium inventory depended 

directly on production schedules and varied over time, from a few kilograms up to several thousand 

kilograms with various enrichments. Nuclear fuel manufacturing ended in 1983. 

Operations in Building 004 included research studies in applied physics and physical chemistry, 

analytical chemistry laboratories that supported nuclear fuel fabrication, operation of the L-77 reactor, 

and operation of the Gamma Irradiation Facility, an above-ground vault in Building 004 that used

sealed Cs-137 and Co-60 sources for radiation-hardening tests of electronic components and food 

irradiation research. GIF activities ceased in the late 1980s; the sources were shipped off-site for 

recycling in the early 1990s. Bi-annual leak checks of GIF sources had determined that none of these 

sealed sources ever leaked (GIF, 2003). In 1995, a Rocketdyne survey of the GIF verified that it was 

not contaminated. The GIF was comprised of Rooms 41M-11 and 41M-11A attached to the northeast

comer of Building 004 (GIF, 2003). 

The L-77 was a small, enriched uranyl sulphate solution research reactor operated in Room 416-61 of 

Building 004. The uranyl sulphate was uranium-enriched to just less than 20% U-235 (Nuclear 

Activities, 1991). The L-77 reactor ceased operation in October 1974. The fuel solution was removed 

in March 1976, and the reactor was decommissioned and disposed of as low-level radioactive waste. 

The operating license was terminated in February 1982 (Nuclear Activities, 1991).
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6.0 Summary of Available Monitoring Data for the Class Evaluated 

by NIOSH

Internal and external radiological monitoring data are available for individual workers at the De Soto 

Avenue Facility. The monitoring was performed and collected by the staff of radiation and nuclear 

safety specialists supporting both De Soto Avenue and Area IV. The centralized record-keeping 

organization maintained records of the monitoring results for the purpose of tracking worker 

exposures for both De Soto Avenue and Area IV workers during the years under evaluation. These 

records do not differentiate monitoring results by facility; therefore, NIOSH can identify an 

individual’s monitoring results but cannot consistently distinguish the results by site since De Soto 

Avenue and Area IV operated contemporaneously. 

The following subsections provide an overview of the state of the available internal and external 

monitoring data for the De Soto Avenue Facility class under evaluation.

6.1 Available De Soto Avenue Facility Internal Monitoring Data

The primary data used for determining internal exposures are derived from personal monitoring data, 

such as urinalyses, fecal samples, and whole-body count (WBC) results. In addition, air monitoring 

data from breathing zone and general area monitoring may be useful to estimate the potential internal 

exposure. Original personal monitoring and breathing zone area monitoring records for De Soto 

Avenue are available to NIOSH, as is source term information in the form of Use Authorization 

documentation created as part of Rockwell’s Isotopes Committee process for controlling radionuclide 

operations. 

As described in Section 5.2.1, the radiological monitoring programs for Area IV and De Soto were 

centralized. Monitoring records do not generally include location indications for the specific site (De 

Soto Avenue or Area IV) where a worker was assigned at the time of sampling. 

Available in vitro bioassay data for De Soto Avenue employees include uranium bioassays and 

sample analyses for gross alpha and gross beta. Available in vivo bioassay data for De Soto 

employees include semi-annual whole-body counts performed by a contracted mobile counting lab 

brought on site. 

Details regarding the various analyses used and the associated minimum detectable activities are 

presented in the Technical Basis Document Area IV of the Santa Susana Field Laboratory, the 

Canoga Avenue Facility (Vanowen Building), the Downey Facility, and thee De Soto Avenue Facility 

(sometimes referred to as Energy Technology Engineering Center [ETEC] or Atomics International)-

Occupational Internal Dose (ORAUT-TKBS-0038-5). 
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6.1.1 In Vitro Monitoring

NIOSH has in vitro radiation dosimetry records: (1) for workers assigned to areas of high surface 

contamination; (2) as requested for specific operations; and (3) for special samples that may have been 

triggered by general workplace air and breathing-zone air samples exceeding site-prescribed 

thresholds. The in vitro bioassay records in the individual radiological exposure files generally 

consist of: 

• individual personnel McBee key-sort cards, which were used to track the type, frequency, and 

week of sample collection (the card summarized individual results); 

• individual analysis result sheets containing all the information on analyses conducted. This form 

might show the calculated result (even if it was below the limit of detection), the sensitivity of the

analysis, and the uncertainty; 

• wound monitoring reports; and 

• individual, hand-drawn or computer-generated plots of bioassay data, apparently done as 

follow-up to high results. 

Uranium urinalyses were performed for fuel-fabrication workers. Gross beta or mixed fission product 

urinalyses were available for workers in jobs having the potential for such exposures. Commercial 

laboratories performed analysis of urine samples. Special samples were requested when an intake was 

suspected, or if a routine sample exceeded 10% of the urinary excretion expected from 1 maximum 

permissible body burden (MPBB). Information on the vendors used by the program and when they 

were employed is available to NIOSH in a bioassay database. The vendors offered the following

sample analysis services: fluorometric and radiometric uranium bioassay, gross alpha, and gross beta. 

(ORAUT-TKBS-0038-5) The bioassay database contains over 37,300 in vitro results from 1949 

through 2008. These 37,300+ results include results from De Soto Avenue workers. The radiation 

safety program supporting the radiological work at De Soto Avenue and Area IV of the SSFL was 

centralized and focused on controlling workplace exposures. The records do not clearly differentiate 

samples for workers at De Soto Avenue from those at Area IV. Developing a count of De Soto 

Avenue-specific results would be labor-intensive, and unless the results were reported as 

radionuclide-specific, the effort would provide little additional information about De Soto-specific

exposures. 

The bioassay vendor laboratories did offer nuclide-specific analyses. The bioassay database includes 

results of samples analyzed for isotopes of cobalt, cesium, polonium, plutonium, strontium, tritium, 

thorium, and mixed fission products. 

Specific, limited operations involving work with thorium occurred at De Soto Avenue. These 

operations are described in some detail in Section 7.2.1.1 of this report. 

From June through July, 1970, De Soto conducted operations involving Transit Capsule testing in two 

rooms of Building 001. A total of 17 or 18 capsules were to be disassembled in the Hot Shop area. 

One machinist and an engineer were assigned to the task. NIOSH has dosimetry records from 1970 

for both individuals, including two thorium urine results for the engineer, and three urine samples and 

one fecal sample for the machinist; all samples were analyzed for thorium mass (μgm). 
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Also during June 1970, De Soto conducted the fabrication of 5 to 10 pieces of thoria-molybdenum 

cermet fuel simulant in two rooms of Building 001 (Meyer, 1970). Analysis of the simulant was to be 

done in a different room in Building 001. Two operators were assigned to the simulant work. NIOSH 

has dosimetry records for those two operators, including two urine samples for each sent to U.S. 

Testing for thorium analysis. One sample was lost by the vendor, so NIOSH has three results related 

to this work. These samples were analyzed for thorium mass (μgm).

The 1979 operation called for grinding the corners off of approximately 540 plates of thorium metal. 

This operation was to be performed in one room in Building 001. One operator was assigned to 

perform the work, with one assistant and a supervisor. NIOSH has dosimetry records for all three 

individuals assigned to the operation, including two thorium urinalysis sample results for the operator, 

one before the job began, and one following job completion. These samples were analyzed for 

thorium mass (μgm). NIOSH also has copies of the Restricted Access Area Entry permit, general air 

sampling data, personal lapel air sampling data for the operator, and contamination survey reports for 

the operations (Grinding Safety, 1979).

During the period from August 1991 through June 1993, the vendor Controls for Environmental 

Pollution provided in vitro bioassay sample analysis services to SSFL, including De Soto Avenue. 

NIOSH does not use CEP sample analysis results to assign dose because CEP was suspected of 

producing unreliable results. In 1991, the site had self-identified concerns with the work products 

from CEP and subsequently was made aware of DOE concerns regarding potential falsification by 

CEP of Sandia National Laboratory bioassay processing. In December 1994 letters to SSFL 

monitored employees (Rockwell, 1994), Rockwell International stated the following: 

• The CEP-related bioassays were all routine and/or baseline samples and none were the result of 

incidents;

• During the period when samples were analyzed by CEP (1991–1993), air sample data were 

routinely taken in work areas to confirm that airborne activity remained below regulatory limits;

• During that same time, the same workers underwent whole-body measurements performed by a 

different contractor (Helgeson), instituted as a separate and independent measure of internal 

exposure; 

• The whole-body measurements showed no measurable exposures; and

• Follow-on samples analyzed by the new in vitro contractor, Teledyne-Brown Engineering, 

confirmed no measurable internal exposure. 

Rockwell concluded their letter with: “In summary, although CEP bioassay results have been 

questioned, independent Helgeson WBS, Teledyne bioassays, and air sampling have confirmed that 

Rocketdyne workers have experienced no measurable internal exposure.” 

As part of its 2017 evaluation of SEC-00235 (NIOSH, 2017), NIOSH determined that the lack of CEP 

in vitro data has not affected NIOSH’s ability to perform sufficiently accurate internal dose 

reconstructions for monitored or unmonitored workers. The data evaluated included monitoring for 

both SSFL Area IV and the De Soto Avenue facilities. NIOSH’s findings for SEC-00235 were based 

on the following: 
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• NIOSH compared remediation period bioassay data to operational period data (through 1988) that 

were used to develop NIOSH’s internal co-worker intake rates. NIOSH saw no indication that the 

co-worker intake rates assigned for the end of the Area IV operation period (circa 1988) do not 

bound the potential remediation period exposures for unmonitored workers. 

• NIOSH examined operations throughout the remediation period (1989–present) to evaluate the 

exposure conditions before, during, and after the CEP period of concern. NIOSH found that work 

remained consistent through the remediation period, and that all major radiological work in the 

CEP period 1991–1993 would have had workplace and/or personnel monitoring also performed 

outside the CEP-related period.

• During the August 1991 through June 1993 period with disqualified CEP bioassay results, the site 

was performing routine in vivo whole-body measurements with a different contractor. The site 

reported that the whole-body measurements showed no measurable exposures. In response to 

concerns with CEP data, the SSFL site also initiated confirmatory resamples analyzed by a new 

contractor, and reported that these follow-up in vitro results confirmed no measurable internal 

exposures. 

6.1.2 In Vivo Monitoring

Helgeson Scientific Services was contracted by the Rocketdyne Division to provide onsite in vivo 

bioassay evaluations of workers every six months. Suspected intakes would have triggered follow-up 

in vitro bioassay sampling, or if the in vivo bioassay vendor was scheduled to be available, a wholebody or other count. Under the routine bioassay program, an in vivo analysis typically would be 

scheduled once every six months for workers with duties in high-contamination areas or airborneradiation areas. In addition to whole-body count results, NIOSH has a limited number of other in vivo 

bioassay results, such as lung, thyroid, and wound counts. The in vivo bioassay reports provided by 

Helgeson Scientific identify the measurements as organ-specific or total-body, and include a table of 

minimum sensitivities for the counter, calibration information, and descriptions of the counting 

equipment in terms of the detector and electronics (Helgeson, 1993). The in vivo monitoring results 

reported by Helgeson for the Rockwell sites included results for radionuclides of uranium, cesium, 

potassium, zinc, and americium for plutonium. Thyroid measurements for radioactive iodine were 

also reported. 

As presented in Section 6.1.1, during the August 1991 through June 1993 period with disqualified 

CEP bioassay results, the site was performing routine in vivo whole-body measurements. The 

monitoring information in employee radiological exposure files included in vivo whole-body 

measurement results. In the 1994 letter to SSFL workers potentially affected by the CEP bioassay 

issue, Rockwell International stated that the scans done during the time of the CEP contract were 

“instituted as a separate, independent measure of internal exposure.” This letter also stated that there 

was “no measurable internal exposure” to the Rocketdyne workers (Rockwell, 1994). This statement 

is supported in the results examined by NIOSH for its 2017 evaluation of SEC-00235, which 

consisted predominantly of non-detectable WBC results (NIOSH, 2017). 
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6.2 Available De Soto Avenue Facility External Monitoring Data

The primary data used for determining external exposures are personal monitoring data from film 

badges or thermoluminescent dosimeters (TLDs). In 1963, the De Soto Avenue Facility began using 

the commercial vendor Landauer’s multi-element film dosimeters with a monthly or quarterly 

exchange frequency. All personnel assigned to operations with potential radiation exposure were 

required to wear personnel monitoring devices, as dictated by the Atomics International radiological 

safety program. Film badges were also available for visitors to controlled areas. Pocket dosimeters 

and finger film rings were issued based on work assignments (Lang, 1960).

External dosimetry data were manually entered into a database for an epidemiological study of 

workers at Rocketdyne (Atomics International) covering the period 1948 to 1999. These data were 

applied for the development of a co-worker analysis. A total of 6,675 workers were monitored for 

radiation exposure and, of those, 5,801 were included in the database. Three hundred-fifty (350) 

workers who were employed for less than six months and 524 workers with insufficient identifying 

information were excluded from the study (ORAUT-OTIB-0077, PDF p. 5). 

Details regarding the various analyses used and the associated minimum detectable activities are 

presented in the Technical Basis Document Area IV of the Santa Susana Field Laboratory, the 

Canoga Avenue Facility (Vanowen Building), the Downey Facility, and thee De Soto Avenue Facility 

(sometimes referred to as Energy Technology Engineering Center [ETEC] or Atomics International)-

Occupational External Dose (ORAUT-TKBS-0038-6). 

7.0 Feasibility of Dose Reconstruction for the Class Evaluated by 

NIOSH

The feasibility determination for the class of employees under evaluation in this report is governed by 

both EEOICPA and 42 C.F.R. § 83.13(c)(1). Under that Act and rule, NIOSH must establish whether 

or not it has access to sufficient information either to estimate the maximum radiation dose for every 

type of cancer for which radiation doses are reconstructed that could have been incurred under 

plausible circumstances by any member of the class, or to estimate the radiation doses to members of 

the class more precisely than a maximum dose estimate. If NIOSH has access to sufficient 

information for either case, NIOSH would then determine that it would be feasible to conduct dose 

reconstructions. 

In determining feasibility, NIOSH begins by evaluating whether current or completed NIOSH dose 

reconstructions demonstrate the feasibility of estimating with sufficient accuracy the potential 

radiation exposures of the class. If the conclusion is one of infeasibility, NIOSH systematically 

evaluates the sufficiency of different types of monitoring data, process and source or source term data, 

which together or individually might assure that NIOSH can estimate either the maximum doses that 

members of the class might have incurred, or more precise quantities that reflect the variability of 

exposures experienced by groups or individual members of the class as summarized in Section 7.6. 

This approach is discussed in NIOSH’s SEC Petition Evaluation Internal Procedures, which are 

available on the NIOSH Radiation Dose Reconstruction Program webpage. 
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The next four major subsections of this evaluation report examine:

• The sufficiency and reliability of the available data. (Section 7.1) 

• The feasibility of reconstructing internal radiation doses. (Section 7.2) 

• The feasibility of reconstructing external radiation doses. (Section 7.3) 

• The bases for petition SEC-00246 as submitted by the petitioner. (Section 7.4) 

7.1 Pedigree of De Soto Avenue Facility Data

This subsection answers questions that need to be asked before performing a feasibility evaluation. 

Data Pedigree addresses the background, history, and origin of the data. It requires looking at site 

methodologies that may have changed over time; primary versus secondary data sources and whether 

they match; and whether data are internally consistent. All these issues form the bedrock of the 

researcher’s confidence and later conclusions about the data’s quality, credibility, reliability, 

representativeness, and sufficiency for determining the feasibility of dose reconstruction. The 

feasibility evaluation presupposes that data pedigree issues have been settled.

Upon request, the facility provides original hardcopy records, including internal and external 

dosimetry records for individual claimants; these records are used by NIOSH to support dose 

reconstruction. 

7.1.1 Internal Monitoring Data Pedigree Review

As described in detail in the co-worker document Internal Coworker Dosimetry Data for Area IV of 

the Santa Susana Field Laboratory and the De Soto Avenue Facility (ORAUT-OTIB-0080, PDF pp. 

8–10), urinalysis bioassay data were obtained directly by NIOSH from SSFL (including De Soto 

records) in the form of electronic scans of hardcopy bioassay data records. These records contain De 

Soto internal monitoring records and records from the analytical laboratories that performed the 

urinalyses. The dosimetry program received urinalysis results data from the vendor laboratories and 

transcribed that data onto internal forms, which were referred to as “8X11” and “McBee cards.” 

These data (digital copies of the original site data) were used to perform the NIOSH co-worker 

analysis that includes the De Soto Avenue Facility. These original data records are considered 

primary data sources; therefore, further consistency checks of the internal data for the period from 

1965 through 1995 are not required. Any bioassay results from the vendor laboratory CEP are

excluded by NIOSH from final consideration due to concerns with vendor product quality. 

NIOSH has determined that the internal radiological monitoring data obtained from the De Soto 

Avenue Facility are of sufficient quantity, and are supported by sufficient information on the internal 

dosimetry program practices, to assure that the data adequately represent the evaluated class.

7.1.2 External Monitoring Data Pedigree Review

Atomics International started using commercial vendors for its dosimetry needs in the early 1960s and 

continued that practice throughout the period under evaluation. Original, individual external 

dosimetry records are available for all workers assigned to jobs that were deemed to have a potential 

for radiation exposure. Those employees were monitored over the period under evaluation in this 
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report. The exchange frequencies for site employees were based on the potential to exceed the 

administrative exposure limits (ORAUT-TKBS-0038-6). The original De Soto personnel records and 

the associated radiological program information are considered primary data sources; therefore, 

further consistency checks of the external data for the period from 1965 through 1995 are not 

required. 

Dosimetry data, including external exposure data, was entered into a database and used to develop the 

external co-worker dosimetry model, ORAUT-OTIB-0077, for assigning doses for gaps in dosimetry 

records. The dosimetry database contains data for penetrating dose, which is a combination of gamma 

and fast neutron dose. Because it was difficult to separate statistically significant neutron dose from 

the penetrating dose, and because shallow dose data are not available, the neutron dose component 

(which represented less than 5% of the total data points available) was left embedded with gamma 

dose, resulting in penetrating dose values that are biased high, especially so for De Soto employees, 

given the lack of neutron exposure potential associated with De Soto work. Exposure information 

was compiled from the following sources: Rocketdyne radiation safety folders, NRC-REIRS, DOEREMS, Landauer dosimetry, individual facilities, the U.S. Army, and the U.S. Air Force. These data 

include results from workers who had duties at the Area IV, Canoga, De Soto Avenue, and Downey 

sites.

NIOSH has determined that the external radiological monitoring data obtained from the De Soto 

Avenue Facility are of sufficient quantity, and are supported by sufficient information on the external 

dosimetry program practices, to assure that the data adequately represent the evaluated class.

7.2 Evaluation of Bounding Internal Radiation Doses at the De Soto Avenue 

Facility

The principal source of internal radiation doses for members of the class under evaluation was 

inhalation or ingestion of uranium associated with nuclear fuel element fabrication. Inhalation or 

ingestion of contamination resulting from operations involving unsealed radioactive material during 

radiochemistry operations was also possible. The following subsections address the ability to bound 

internal doses, methods for bounding doses, and the feasibility of internal dose reconstruction.

7.2.1 Evaluation of Bounding Process-Related Internal Doses

The petition bases for SEC-00246 requested that NIOSH consider for inclusion into the SEC all 

workers who worked at the De Soto Avenue Facility from January 1, 1965 through December 31, 

1995. The basis for SEC inclusion was partially based on the assertion that operations conducted at 

the De Soto site: (1) involved contractors and subcontractors shared with Area IV of the SSFL; and 

(2) involved the same hazards for which NIOSH determined it was unable to reconstruct radiation 

dose with sufficient accuracy for Area IV (i.e., occupational exposure to americium and thorium and 

its associated progeny) from January 1, 1965 through December 31, 1988. 

SSFL established and maintained a centralized radiological records program that contains the records 

and data for De Soto Avenue, Area IV, Canoga Avenue, and Downey. The health physics records and 

source term and process information, including types and quantities of specific radionuclides and 

sources present, their chemical and physical form, and the types and frequency of operations 

(including controls) in which these sources were used are available to NIOSH as original records. 
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The following have been identified as radionuclides of concern for internal dose for the De Soto 

Avenue during the period under evaluation (see also Section 5.2): 

• Uranium: Through the course of ongoing dose reconstruction efforts and investigations, NIOSH 

determined that although internal monitoring data are available for most radiological workers at 

De Soto, some employees could have received internal radiation exposures that went unmonitored. 

To assess potential internal uranium dose to unmonitored employees, NIOSH developed a coworker dose distribution model, Internal Coworker Dosimetry Data for Area IV of the Santa 

Susana Field Laboratory and the De Soto Avenue Facility (ORAUT-OTIB-0080). 

As presented in Section 5.2.1, briquettes of a 93% enriched uranium and aluminum alloy known 

as uranium aluminide were handled at De Soto in association with ATR fuel-fabrication 

operations from 1966 to 1968. These De Soto UAlx exposures are potentially more limiting than 

uranium exposures evaluated with standard uranium metabolic models. NIOSH considers these 

potential uranium aluminide exposures to be the bounding uranium exposures at the De Soto 

Avenue Facility.

Attachment H of ORAUT-TKBS-0038-5 presents modifications to the International Commission 

on Radiological Protection (ICRP) Publication 66 human-respiratory-tract model (HRTM), 

originally proposed in 2005 (Leggett, 2005), that specifically addresses the biokinetics of uranium 

aluminide (ICRP, 1994). This modification, referred to as Type K (versus Type F, M, or S) 

material, was based on occupational bioassay data collected at the Rocketdyne/Atomics 

International Facility in California and fits the site-specific excretion data. The alternate methods 

described in Attachment H of ORAUT-TKBS-0038-5 are available to NIOSH to ensure that 

bounding uranium dose calculations are applied to De Soto Avenue work for the period under 

evaluation. 

• Americium: During its document review, NIOSH found that Atomics International held a State of 

California Department of Public Health Radioactive Material License (0015-59) authorizing the 

De Soto site to have up to 10 Ci of Am-241 in any form for the purpose of sealed-source 

fabrication and transfer to authorized recipients (License, 1978); however, neither the document 

review nor interviews with former workers revealed any history of actual fabrication of americium 

sources (Personal Communication, 2018a; Personal Communication, 2018b). When NIOSH 

evaluated SEC-00234 for Area IV, it determined that a significant factor causing uncertainty 

regarding the accuracy of dose reconstruction was the lack of well-defined source term 

information for americium produced during Area IV reactor operations over time. NIOSH has 

found that no similar source term existed at the De Soto Avenue Facility. De Soto did not use 

americium sources in any work processes. On the other hand, De Soto had well-defined sources 

of the radionuclide thorium. Much of the source term information for De Soto is available through 

site records and licensing documentation. 

• Thorium: As referred to in Section 5.2.1.2, three specific, limited operations involving work with 

thorium occurred at De Soto Avenue. These operations are detailed in use-authorization 

documentation and procedures maintained by the site and are available to NIOSH. 

The first of these tasks, documented as Authorization 13 (Authorization, May1970), occurred in 

June 1970 and entailed the fabrication of simulated fuel discs made from molybdenum and natural 

thorium. The work was limited to 5 kg of ThO2 powder in granular form, and the powder 

underwent particle-sizing, blending, and preparation for cold-pressing. All of this powder work, 
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the particle-sizing work, and the packaging and removal of the powder was conducted in glove 

boxes under negative pressure in Room 119-62 of Building 001. The ThO2 powder was ballmilled with molybdenum metal powder in Room 119-62 to coat the powder grains. The coldpress occurred in an enclosure with radioactive exhaust, also in Room 119-62. The cold-pressed 

discs would then undergo sintering and either hot pressing or explosive forming. Hot-pressing 

occurred in Room 524-59 of Building 005. The discs were never to leave the outer transport 

containers, were to be removed from the building every night and were not to be in the building 

over two hours. Explosive-forming occurred off-site at a facility known as El Toro. The 

procedures for sizing, blending, cold-press, and sintering are available for review (Authorization, 

May1970).

The second of these tasks, documented as Authorization 21 (Authorization, Jun1970) involved 

analysis following design verification testing done at Sandia National Laboratories (SNL), for 

which the simulated fuel discs were created. This work occurred in June and July 1970. These 

2.5” x 6” transit capsules were tested at Sandia for impact, fragmentation, over-pressure, and fire 

durability. Following this testing at Sandia, the transit capsules were delivered to De Soto 

Avenue for post-test analysis. This De Soto analysis entailed non-destructive testing, then 

disassembly of the transit capsules and removal of the ThO2 cermet simulated fuel discs. The 

simulated fuel discs were removed in a plexiglass box enclosure, packaged, and shipped to the Los 

Alamos Scientific Laboratory (LASL). The post-test examination procedures are available 

(Authorization, Jun1970, PDF pp. 33-35). 

The last of these tasks associated with thorium was the machining of thorium metal discs. This 

operation is documented as Authorization 120 (Tuttle, 1979; Begley, 1979). The machining work 

involved grinding off the corners of approximately 540 plates (~ 200 kg) of natural-thorium metal. 

The plates were to be stacked 10-20 at a time, and each corner ground by multiple passes on a 

surface grinder. The work was performed in one room, Room 115-37 of Building 001. As 

documented in the internal memo, Review of Proposal to Machine Thorium (Tuttle, 1979), an 

enclosure and chip catcher were to be attached to the grinding head and a HEPA-filtered vacuum 

cleaner was to be attached to the enclosure to remove dust, fumes, and gas released by the 

grinding. The filtered vacuum cleaner failed to maintain adequate air flow (Begley, 1979) and a 

change authorization was granted to modify the procedure to “wet” grinding. A recirculating 

water tank was installed, along with a Plexiglas shield between the grinding operation and the 

operator. The HEPA-filtered vacuum continued to be used. 

Fabrication of the simulated fuel discs was assigned to two individuals; operations involving loose 

material were to be contained within a glove box. The Transit Capsule Post-test analysis involved 

disassembly in the Hot Shop area of approximately 17 or 18 capsules containing simulated fuel 

discs. One machinist and an engineer were assigned to the task. Disrupting the solid nature of the 

fuel discs was a hazard to be mitigated rather than an expected part of the operation. Efforts were 

undertaken to contain the fuel discs and prevent breaching them. 

The work of grinding thorium-metal plates was necessarily performed in the open with a devised 

enclosure and chip catcher. One operator with an assistant and a supervisor were assigned to this 

task, which occurred in one room of Building 001. 

This last operation in 1979, the grinding of the plates, appears to have the highest potential of the 

three for thorium intake by inhalation because it was not performed in a glove box or similarlyconfined space and involved mechanical operations likely to dislodge respirable particles of 
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thorium into the work space. This operation is considered by NIOSH to have the highest exposure 

potential of the three thorium operations at De Soto. The dosimetry records for the workers 

assigned to all three of these operations are available to NIOSH and summarized in Section 6.1.1. 

Methods for assigning bounding thorium doses are described further in Section 7.2.3. 

The following subsections summarize the extent and limitations of information available for 

reconstructing the process-related internal doses of members of the class under evaluation.

7.2.1.1 Urinalysis Information and Available Data 

Uranium bioassay results for De Soto Avenue are presented in the records as fluorometric (mass) and 

radiometric (activity) results. Samples analyzed fluorometrically were also analyzed radiometrically. 

The site used both zeros and “less-than” values to indicate non-detectable results. In addition to 

analyzing bioassay samples for uranium, the site performed some gross-alpha sample analysis. 

Sufficient urine bioassay data were available to perform a statistical analysis for 1965 through 1988 as 

part of the internal dose co-worker analysis (ORAUT-OTIB-0080). Uranium bioassay data are 

available through the end of fuel fabrication work (1983) for monitored workers. 

Pre-work and post-work thorium urine bioassay was performed for workers conducting the 1979 

thorium-grinding operations, as identified in the authorization paperwork approved by the De Soto 

Isotopes Committee (Tuttle, 1979; Begley, 1979). The samples were sent off site to a commercial 

vendor for analysis. The thorium bioassay results correspond directly to the names and dates of the 

operation as specified in the authorization documentation, which also specifies the task scope and 

natural thorium materials for these limited thorium operations. Those records are available to NIOSH. 

NIOSH found no records of any urine bioassay analysis for americium associated with the De Soto 

Avenue Facility, nor any evidence of americium exposure conditions, as presented above. 

As presented in Section 6.1.1, NIOSH does not use CEP sample analysis results to assign dose 

because CEP was suspected of producing unreliable results. Although NIOSH has disqualified in 

vitro data analyzed by CEP during the period August 1991 through June 1993, in its 2017 evaluation 

of SEC-00235 (NIOSH, 2017), NIOSH determined that the lack of CEP in vitro data has not affected 

NIOSH’s ability to perform sufficiently accurate internal dose reconstructions for monitored or 

unmonitored workers. The current NIOSH findings for the De Soto Avenue Facility are consistent 

with its 2017 evaluation for Area IV of SSFL and are based on the following: 

• NIOSH examined the radiological operations throughout the period under evaluation (1965-1995) 

to ascertain the exposure conditions before, during, and after the CEP period being evaluated in 

this report (1991–1993). NIOSH’s review indicates that work remained consistent as to 

procedures, personnel protection equipment, and exposure risks from 1984 (when most 

radiological activities had ceased) through 1995 (when all radiological activities ceased). NIOSH 

has found no major radiological project that occurred in the CEP period 1991–1993, that would 

not have had workplace and/or personnel monitoring performed outside the CEP-related period. 

• During the August 1991 through June 1993 period with disqualified CEP bioassay results, the site 

was performing routine in vivo whole-body measurements with the contractor Helgeson. The site 

reported that the whole-body measurements showed no measurable exposures.
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• In response to concerns with CEP data, the site health and safety program initiated confirmatory 

resamples analyzed by a new contractor. These follow-up in vitro results confirmed no 

measurable internal exposures.

The site’s investigation was summarized in December 1993 as, “... although CEP bioassay results 

have been questioned, independent Helgeson WBS, Teledyne bioassays, and air sampling have 

confirmed that Rocketdyne workers have experienced no measurable internal exposure.” (Rockwell, 

1994). 

NIOSH researched the operations at De Soto Avenue to determine if any significant factors affecting 

potential exposures or monitoring might have changed during the 1991 through 1993 period when the 

CEP in vitro bioassay analyses were deemed unreliable. No changes in operations were identified; 

radiological operations were limited to Building 004 during this time and at a reduced level. The 

other aspects of the radiation monitoring program at De Soto Avenue, the in vivo monitoring with the 

contractor Helgeson, the air sampling, and the area monitoring continued unchanged. 

7.2.1.2 WBC Measurement Information and Available Data 

The monitoring information in the employee radiological exposure files described in this report also 

included WBC monitoring information and results. The WBC measurements for both De Soto and 

Area IV workers were performed by Helgeson, using mobile scanner facilities brought on site by the 

contractor. The results provided were entered in the worker’s radiological exposure files. The in vivo

monitoring results reported by Helgeson for the Rockwell sites included results for radionuclides of 

uranium, cesium, potassium, zinc, and americium for plutonium. Thyroid measurements for 

radioactive iodine were also reported. There is no indication that the site made an attempt to quantify 

thorium through in vivo measurements of thorium progeny radionuclides. 

In the 1994 letter to workers potentially affected by a lack of confidence in CEP data (discussed in 

Section 7.2.1.1), Rockwell International stated that the WBC monitoring done during the time of the 

CEP contract were “instituted as a separate, independent measure of internal exposure.” This letter 

also stated that there was “no measurable internal exposure” to the Rocketdyne workers (Rockwell, 

1994). This statement is supported in the results, which consisted predominantly of WBC results with 

no detectable activity. 

7.2.1.3 Other Types of Bioassay

Some results presented with volume or mass units of grams are assumed to be fecal samples. At least 

one instance of a thorium bioassay sample is noted to be a fecal sample. 

7.2.1.4 Airborne Levels 

NIOSH has access to workplace air monitoring data including, in limited cases, lapel air monitoring 

results (including lapel results for thorium work in 1970 and 1979). Generally, jobs that necessitated 

an Authorization for Use of Radioactive Materials or Radiation Producing Devices were monitored, 

and if there was a potential for inhalation by workers, personal lapel air monitoring was required. 

Other work required air monitoring. A random sampling of the employee folders obtained for the 

co-worker calculations found no indications of those air sample results being included in the employee 

files. A targeted review of employee files for workers specifically assigned to thorium-machining 

work did reveal job-specific air sample worksheet results. Operations such as the thorium grinding, 
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and work with thoria materials in powder form, are likely to be bounding exposure scenarios. Air 

sample results, collected in proximity to thorium-grinding operations, support the ability to develop a 

bounding dose estimate for potential thorium intakes. 

7.2.2 Evaluation of Bounding Ambient Environmental Internal Doses

NIOSH has access to environmental monitoring data, including air emissions and ambient air 

monitoring data. An environmental monitoring program was established in May 1954 (SSFL Site, 

2005). The program initially placed an emphasis on soil, vegetation, and water sampling in the 

environment (SRDB TKBS-0038-4); but beginning in 1959, ambient gross beta activity in air was 

measured continuously in five locations. De Soto Avenue ambient air monitoring data are reported in 

Annual Review of Radiological Controls reports, available to NIOSH (Annual Review, 1975; Annual 

Review, 1976; Annual Review, 1977; Annual Review, 1978; Annual Review, 1979; Annual Review, 

1980; Annual Review, 1981; Annual Review, 1982; Annual Review, 1983; Annual Review, 1984; 

Annual Review, 1985; Annual Review, 1986; Annual Review, 1987; Annual Review, 1988). 

Ambient air sampling for long-lived particulate alpha and beta radioactivity was performed 

continuously by automatic sequential samplers located at De Soto and SSFL. Air was drawn through 

glass-fiber filters, which were analyzed for retained long-lived radioactivity after a minimum 120-h 

decay period, which eliminated naturally-occurring short-lived particulate radioactivity (most radon 

daughters). 

The guide value of 3 x 10-12 μCi/ml for De Soto Avenue ambient air alpha activity was due to prior 

work with unencapsulated depleted uranium. The guide value of 3 x 10-l0 μCi/ml was for Co-60. This 

was chosen as an appropriate ambient air beta activity guide since it was the most restrictive limit for 

any beta-emitting radionuclides in use at De Soto Avenue. 

Air sampling was performed continuously at De Soto and SSFL with air samplers operating on 24-hr 

sampling cycles. Airborne particulate radioactivity was collected on glass-fiber filters which were 

automatically changed daily at the end of each sampling period (midnight). The samples were 

counted for alpha and beta radiation following a minimum 120-hr decay period. The volume of a 

typical daily ambient air sample was about 25 m3

 (Monitoring Report, 1989). 

The ambient air monitoring data through 1999 are reported in the environmental monitoring reports as 

gross alpha and gross beta without identification of specific radionuclides (ORAUT-TKBS-0038-4, 

PDF p. 10). In all cases, the gross alpha and gross beta concentrations are a small fraction of the 

applicable limits and are indistinguishable from background. Because of this, NIOSH uses stack 

emission data as the primary basis for inhalation intake estimates from onsite atmospheric 

radionuclide concentrations. Stack-emission data are available for Building 004/104 (Hot Analytical 

Chemistry at the De Soto Avenue Facility). TBD Table 4-3, Annual Occupational Environmental 

Radionuclide Inhalation at De Soto Avenue, Canoga Avenue, and Downey Facilities (ORAUT-TKBS0038-4, PDF p. 13), lists the estimated environmental inhalation intakes at De Soto Avenue, Canoga, 

and Downey by year and radionuclide. All data in the table for the period under evaluation (1965 

through 1995) would be De Soto Avenue data given that only De Soto Avenue had radiological work 

by that time. 
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7.2.3 Methods for Bounding Internal Dose at the De Soto Avenue Facility

The following subsections summarize the methods for bounding internal dose at the De Soto Avenue 

facility. 

7.2.3.1 Methods for Bounding Operational Period Internal Dose

Internal doses for monitored workers are assigned in accordance with ORAUT-TKBS-0038-5, TBD 

for the Area IV of the Santa Susana Field Laboratory, the Canoga Avenue Facility (Vanowen 

Building), the Downey Facility, and the De Soto Avenue Facility (Sometimes Referred to as Energy 

Technology Engineering Ctr. [ETEC] or Atomics International)– Occupational Internal Dose. 

Some workers at De Soto Avenue were not monitored for potential intakes to radioactive material 

because, in the assessment of the facility health physicist, their job assignment was unlikely to have 

the potential for intake of significant radiological materials. If the job assignment was not in a 

high-contamination area or an airborne radioactivity area, the workers were generally unmonitored for 

internal exposure (Personal Communication, 2017). The NIOSH co-worker study, initiated to address 

potentially-unmonitored workers at Area IV and De Soto Avenue, used urinalysis results of monitored 

workers obtained directly from SSFL in 2009 to assign internal dose to address potential intakes of 

radioactive material. The data and how they were processed are described in ORAUT-OTIB-0080. 

Analyte results were documented in the monitored-employee radiological exposure files obtained 

from the site, including the results of various analytical methods for uranium, plutonium, and mixed 

fission products (MFP). A statistical analysis of the data was performed according to ORAUT-OTIB0019, Analysis of Coworker Bioassay Data for Internal Dose Assignment, ORAUT-PROC-0095, 

Generating Summary Statistics for Coworker Bioassay Data, and the statistical methods in ORAUTRPRT-0053, Analysis of Stratified Coworker Datasets. The results were entered into the Integrated 

Modules for Bioassay Analysis (IMBA) computer program to obtain intake rates for the assignment of 

dose distributions. 

Uranium 

As presented in Section 7.2.1, work with briquettes of uranium aluminide for ATR fuel-fabrication 

operations from 1966 to 1968 have been determined to be the limiting uranium exposure scenario at 

the De Soto Avenue Facility. Attachment H of ORAUT-TKBS-0038-5 presents modifications to the 

biokinetic modelling of uranium aluminide (referred to as Type K) that are based on occupational 

bioassay data collected at the Rocketdyne/Atomics International Facility in California. Attachment H 

examines the dose to organs from various exposure scenarios to determine if and when Type K 

uranium delivers a dose that is higher than the dose from the Type F, M, or S uranium modeled in 

ORAUT-OTIB-0080. Potential intakes of uranium aluminide can be assessed on a case-by-case basis 

using claim-specific and/or fuel fabrication worker-specific data and exposure scenarios; in which

case, NIOSH performs custom case-by-case dose assessments with Type K metabolic modelling. 

Americium

As presented in Sections 5.2.1.1 and 7.2.1, neither the documents available to NIOSH nor interviews 

with former workers (Personal Communication, 2018a; Personal Communication, 2018b) revealed 

any history of fabrication of americium sources, or work with uncontained americium at the De Soto 

Avenue Facility. Contrasting previous NIOSH evaluations of radiological work at Area IV of SSFL, 
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NIOSH has found no indication that De Soto had sources of americium associated with work 

processes.

Thorium 

As presented earlier in Section 7.2, based on the well-described work conditions, with limited 

containment and the potential for generation of airborne thorium contamination, NIOSH has 

concluded that thorium-grinding operations in 1979 represent the bounding thorium internal exposures 

at the De Soto Avenue Facility during the operational period (January 1, 1965 through December 31, 

1995). NIOSH has available pre-work and post-work thorium urine bioassay performed for the single 

worker conducting the 1979 thorium-grinding operations, and the bioassay results correspond directly 

to the name and dates shown in the work authorization documentation. NIOSH has sufficient 

personnel bioassay data, and job performance data, to allow it to develop bounding dose estimates for 

workers with potential thorium exposures during the period from January 1, 1965 through December 

31, 1995. 

Job-specific documentation and pre- and post-work bioassay sample results allow NIOSH to calculate 

bounding organ doses associated with the eight-day grinding operations on natural thorium metal in 

March 1979 (Grinding Safety, 1979). Job-specific information available to NIOSH includes: 

• chronic intake over the period of grinding operations, March 5, 1979 through March 12, 1979; 

• natural thorium metal in equilibrium (assuming 100% Th-232 for intake assessment, and 

50% / 50% Th-228 and Th-232 for dose assessment);

• pre-work urine sample on February 27, 1979 with a result of <0.99 thorium μg per 24-hour 

sample; and

• post-work urine sample on March 25, 1979 with a result of <0.99 thorium μg per 24-hour sample. 

NIOSH estimates under these observed and plausible bounding conditions result in calculated thorium 

intake rates of 7.29E+02 pCi/day for an assumed Type M inhalation, and 4.19E+02 pCi/day for an 

assumed Type S inhalation. NIOSH has sufficient data to assign comparable thorium intake rates to 

De Soto Avenue workers, as appropriate for given job descriptions and potential exposure scenarios. 

7.2.3.2 Methods for Bounding Ambient Environmental Internal Dose

NIOSH has access to environmental monitoring data, including air emissions and ambient air 

monitoring. Potential inhalation intakes from onsite atmospheric radionuclide concentrations can be 

estimated using average annual concentrations of facility stack emissions (ORAUT-TKBS-0038-4). 

Isotopic stack emission data from various facilities for 1988-1999 are available and the data were used 

to characterize radionuclide emissions for all years (ORAUT-TKBS-0038-4). 1988 appears to be 

when isotopic analysis of stack and ambient emissions began. Both americium and thorium were 

analytes. Potential inhalation intakes from onsite atmospheric radionuclide concentrations can be 

estimated using average annual concentrations of facility stack emissions (ORAUT-TKBS-0038-4). 

The average annual stack effluent concentrations described in the site profile (ORAUT-TKBS-0038-

4) are used as the basis for estimating occupational environmental inhalation intakes from facility 

effluent releases. The facility effluent concentrations for each year were summed. Workers were 
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assumed to be exposed for 2,000 hr/yr with a breathing rate of 3.3 × 10-4 m3

/s (ICRP, 1975). Because 

the stack effluent concentrations were sampled at the point of release, a further reduction factor of 

0.01 was taken to account for the lessened overall intake due to contribution from multiple 

widely-spaced facilities, atmospheric dispersion of stack effluent over the course of a year’s exposure, 

and building wake effects.

7.2.4 Internal Dose Reconstruction Feasibility Conclusion

As presented in Section 7.2, the principal source of internal radiation doses for members of the class 

under evaluation was inhalation or ingestion of uranium associated with nuclear fuel-element 

fabrication, or of contamination resulting from radiochemistry operations involving unsealed 

radioactive material. Also evaluated in this report was the potential for worker exposures to 

americium and thorium at the De Soto Avenue Facility. NIOSH has evaluated the issues for which 

this SEC-00246 petition qualified for evaluation and finds that NIOSH has sufficient information to 

allow it to complete sufficiently accurate dose reconstructions for the evaluated class of employees. 

NIOSH has determined that exposures to De Soto workers while working with briquettes of uranium 

aluminide (in association with ATR fuel-fabrication operations from 1966 to 1968) are potentially 

more limiting than uranium exposures evaluated with standard uranium metabolic models. 

Attachment H of ORAUT-TKBS-0038-5 presents modifications to the biokinetic modelling of 

uranium aluminide (referred to as Type K) that are based on occupational bioassay data collected at 

the Rocketdyne/Atomics International Facility in California. NIOSH has examined the dose to organs 

from various exposure scenarios to determine if and when Type K uranium delivers a dose that is 

higher than the dose from the Type F, M, or S uranium modeled in ORAUT-OTIB-0080. Potential 

acute intakes of uranium aluminide can be assessed on a case-by-case basis using claim-specific data 

and exposure scenarios; in which case, NIOSH performs custom case-by-case dose assessments with 

Type K metabolic modelling. 

As presented in Section 7.2.1, neither the documents available to NIOSH nor interviews with former 

workers (Personal Communication, 2018a; Personal Communication, 2018b) revealed any history of 

fabrication of americium sources, or work with uncontained americium at the De Soto Avenue 

Facility. Contrasting previous NIOSH evaluations of radiological work at Area IV of SSFL, NIOSH 

has found no indication that De Soto had sources of americium associated with work processes.

NIOSH has identified detailed documentation of thorium work episodes in 1970 and 1979, providing 

source term, operational procedures, radiological protection protocols, names of individual operators, 

and dates of work. NIOSH has concluded that thorium-grinding operations in 1979 represent the 

bounding thorium internal exposures at the De Soto Avenue Facility during the operational period 

(January 1, 1965 through December 31, 1995). As presented in Section 7.2.3.1, NIOSH has sufficient 

personnel bioassay data (including per-work and post-work urinalysis), and job performance data, to 

allow it to develop a bounding dose estimate for workers with potential thorium exposures during the 

period from January 1, 1965 through December 31, 1995. 

Although NIOSH has disqualified in vitro data analyzed by CEP during the period August 1991 

through June 1993, in its 2017 evaluation of SEC-00235 (NIOSH, 2017), NIOSH determined that the 

lack of CEP in vitro data has not affected NIOSH’s ability to perform sufficiently accurate internal 

dose reconstructions for monitored or unmonitored workers. As presented in Section 7.2.1.1, the 

current NIOSH findings for the De Soto Avenue Facility are consistent with its 2017 evaluation for 

Area IV of SSFL. NIOSH has determined that the exclusion of CEP data during the period 
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1991-1993 does not limit NIOSH’s ability to perform sufficiently adequate internal dose 

reconstructions for De Soto Avenue workers during the period under evaluation. 

Based on its full research of the class under evaluation, NIOSH found no part of said class for which it 

cannot estimate radiation doses with sufficient accuracy, including potential exposures to americium, 

thorium, and uranium. This class includes: all employees of the Department of Energy, its 

predecessor agencies, and their contractors and subcontractors who worked at the De Soto Avenue 

Facility, Canoga Park, California, from January 1, 1965 through December 31, 1995. 

7.3 Evaluation of Bounding External Radiation Doses at the De Soto Avenue 

Facility

The principal source of external radiation doses for members of the evaluated class was exposure 

during fabrication of reactor fuel and radioactive sources used for gamma irradiation. 

The following subsections address the ability to bound external doses, methods for bounding doses, 

and the feasibility of external radiation dose reconstruction. 

7.3.1 Evaluation of Bounding Process-Related External Doses

NIOSH can bound De Soto Avenue workers’ external doses during the period under evaluation 

(January 1, 1965 through December 31, 1995) by using the data described in Section 6.2 of this report. 

NIOSH has captured external monitoring data for De Soto workers for the entire period of this 

evaluation. 

The following subsections summarize the extent and limitations of information available for 

reconstructing the process-related external doses of members of the class under evaluation.

7.3.1.1 Employee Dosimetry Data

NIOSH has access to photon, beta, and neutron external dosimetry results, as well as other supporting 

data for the entire period under evaluation. The policy at De Soto, Area IV, and Canoga Ave. was to 

assign the applicable dosimetry to anyone with the potential for photon, beta, or neutron exposure. 

Dosimetry was assigned based on job assignments that entailed exposure to radioactive materials. 

Details regarding the various analyses used, and the associated minimum detectable activities, are 

presented in ORAUT-TKBS-0038-6. 

The external dosimetry database for the SSFL, which includes De Soto Avenue, contains dosimetry 

data for penetrating dose, including gamma and fast neutron dose. Because it was difficult to separate 

statistically-significant neutron dose from penetrating dose, the neutron dose component (which 

represented less than 5% of the total data points available) was left embedded with gamma dose, 

resulting in penetrating dose values that are conservatively-biased high. An analysis of average 

neutron dose for the period 1965-1995 revealed that the average value for any individual year was 

bounded by the 95th percentile values for penetrating dose given in ORAUT-OTIB-0077. 

7.3.1.2 Area Monitoring Data 

External radiation exposure at the De Soto Avenue Facility would be limited primarily to the vicinity 

of the reactor fuel fabrication and the area near radioactive sources used for gamma irradiation. 
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NIOSH has access to general process and radiological source term information associated with uranium 

fuel-fabrication work, and for radiological projects authorized by the control mechanisms at the site (i.e., 

Isotopes Committee), as documented in the Use Authorization documents. NIOSH has summary data on 

employee exposures, area radiation levels, and in-plant airborne radioactivity sample information for 

operations, found in the reports routinely produced by the site, Annual Review of Radiological Controls, 

for the years 1975-1988 (Annual Review, 1975; Annual Review, 1976; Annual Review, 1977; Annual 

Review, 1978; Annual Review, 1979; Annual Review, 1980; Annual Review, 1981; Annual Review, 

1982; Annual Review, 1983; Annual Review, 1984; Annual Review, 1985; Annual Review, 1986; 

Annual Review, 1987; Annual Review, 1988). The reports contain De Soto Avenue “location badge” 

data only through 1983, when the fuel-fabrication facility was decommissioned. The average and 

maximum exposure rates, determined by quarter, are reported. These reports were produced to satisfy the 

requirements of the special nuclear material license. The reports, which also summarize unusual events 

and provide trend information on exposures, were reviewed by NIOSH. No significant unusual conditions 

were identified upon review. These data are available for use on a case-by-case basis, if necessary, if 

external dosimetry data are unavailable and the co-worker dose estimate is deemed not applicable.

7.3.1.3 Alternative Data Sources for Bounding External Dose

Over the course of ongoing dose reconstruction efforts and investigations associated with both 

SEC-00093 and SEC-00156, NIOSH determined that although external monitoring data are available 

for most radiological workers, some employees could have received external radiation exposures that 

went unmonitored. To assess potential external dose to unmonitored employees, NIOSH developed a 

co-worker dose distribution model, External Coworker Dosimetry Data for Area IV of the Santa 

Susana Field Laboratory, the Canoga Avenue Facility (Vanowen Building), the Downey Facility, and 

the De Soto Avenue Facility (sometimes referred to as Energy Technology Engineering Center 

[ETEC] or Atomics International) (ORAUT-OTIB-0077). This evaluation report has not identified 

any concerns with the external co-worker dose distribution models presented in ORAUT-OTIB-0077. 

7.3.2 Evaluation of Bounding Ambient Environmental External Doses

As presented in ORAUT-TKBS-0038-4, Area IV of the Santa Susana Field Laboratory, the Canoga 

Avenue Facility (Vanowen Building), the Downey Facility, and the De Soto Avenue Facility 

(sometimes referred to as Energy Technology Engineering Center [ETEC] or Atomics 

International)—Occupational Environmental Dose, baseline ambient external radiation dose estimates 

for De Soto Avenue are available for the period 1959 through 1998. From 1974 through 1989 the 

ambient radiation monitoring program used complex bulb dosimeters (CaF2:Mn). This was justified 

by the amount of nuclear materials handled in the operations at De Soto Avenue, and by the low levels 

of radiation in the environment. ORAUT-TKBS-0038-4, Table 4-4 presents annual external 

occupational environmental dose estimates in mrem/yr for De Soto, both baseline doses for the site 

and doses specific for Building 001. 

Routinely, the site produced an Environmental Monitoring and Facility Effluent Annual Report for 

De Soto Avenue and the SSFL sites. Environmental monitoring was performed by the Radiation and 

Nuclear Safety Group of the health and safety organization. Environmental media sampling, air 

sampling, and direct radiation monitoring results were reported in detail. NIOSH has access to these 

semiannual and annual reports for multiple years during this period under evaluation (1965, 1967-

1969, 1971-1972, 1982, 1985, and 1989-1992). 
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Environmental sampling stations located within the De Soto and SSFL boundaries are referred to as 

"on-site" stations. On-site-ambient radiation monitoring using thermoluminescent dosimetry (TLD) 

was used to measure environmental radiation levels at the De Soto Avenue site and also at several 

off-site locations. 

Estimates of the external radiation exposure at the De Soto boundary (less than 0.01 ± 0.01 mR), and 

at the nearest residence (less than 0.01 ± 0.01 mR), are based on the difference between the single 

highest on-site TLD measurement and the average of off-site measurements. The difference is more 

likely the result of random variability in the measurements than from actual radiation exposure.

By 1989, in light of the reduced radiological work, the level of personnel, area, and ambient 

environmental monitoring was no longer justified and efforts were directed toward simplifying the 

program. The initial step included using the well-established LiF thermoluminescent dosimeters 

(TLDs) for personnel monitoring in radiation work. Although these dosimeters were well-suited to 

measuring exposures in the range of interest for compliance with occupational radiation regulations 

(i.e., doses above background), they were somewhat insensitive for environmental measurements 

because the resolution in terms of dose uses increments of 10 mrem/quarter. Using these dosimeters 

demonstrated that environmental exposures did not reach regulatory limits, but it provided limited 

information on the actual exposure rates around the facilities and in the neighboring environment 

(Environmental Report, 1998).

7.3.3 De Soto Avenue Facility Occupational X-Ray Examinations 

In its previous SEC class designation for De Soto Avenue, NIOSH found adequate medical dose 

reconstruction feasible. This current evaluation has found no evidence to the contrary for the period 

under evaluation, January 1, 1965 through December 31, 1995. NIOSH has determined that it is 

feasible to reconstruct occupational medical dose for De Soto Avenue workers for the period from 

January 1, 1965 through December 31, 1995, using information and methods in Dose Reconstruction 

from Occupationally Related Diagnostic X-Ray Procedures (ORAUT-OTIB-0006) and the site profile 

documents (ORAUT-TKBS-0038-1,-2, -3, -4, -5, -6) associated with the De Soto Avenue Facility. 

7.3.4 Methods for Bounding External Dose at the De Soto Avenue Facility

NIOSH has an established protocol for assessing external exposure when performing dose 

reconstructions (these protocol steps are discussed in the following subsections): 

• Photon Dose 

• Beta Dose

• Neutron Dose 

• Medical X-ray Dose (as applicable per Section 7.3.3) 

7.3.4.1 Methods for Bounding Operational Period External Dose

Electron and Photon Dose 

The primary method for assessing photon and beta dose is the use of individual external dosimetry 

records provided by DOE. De Soto Avenue, as part of the SSFL, began using commercial vendors for 

external dosimetry in the 1960s and continued that practice throughout its operations. Landauer was 

the site vendor for external radiation dosimetry services from 1963 through the end of the period 
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under evaluation (1995). A multi-element film dosimeter, exchanged on a known frequency and with 

documented thresholds was the dosimeter for the external monitoring program. The thresholds and 

exchange frequencies are documented in the TBD for external dose, ORAUT-TKBS-0038-6. Missed 

dose will be applied using the protocols documented in External Coworker Dosimetry Data for Area 

IV of the Santa Susana Field Laboratory, the Canoga Avenue Facility (Vanowen Building), and the 

De Soto Avenue Facility (sometimes referred to as Energy Technology Engineering Center [ETEC] or 

Atomics International) (ORAUT-OTIB-0077).

Neutron Dose 

Neutron doses were measured with neutron track analysis, type A (NTA) film from 1954 through 

1989. Both fast and thermal neutrons were measured and recorded as whole-body (WB) dose in rem. 

The NTA film is not effective at energies <0.5 MeV or at exposures of <50 mrem (ORAUT-TKBS0014-6). However, cadmium and lead filters over the beta-gamma film were included in the film 

holder. The difference in densities behind these filters provided a means of detecting thermal neutrons 

via a neutron-gamma reaction in the cadmium filter. The thermal neutron dose, if any, was included 

with the dose detected by the NTA film. It has not been determined what quality factors (QFs) were 

used. However, because a Po-Be neutron source was used for calibration, a reasonable assumption 

would be QF = 10 (ORAUT-TKBS-0038-6, PDF pp. 8-9). 

Medical X-ray Dose 

NIOSH has determined that occupational medical doses can be reconstructed. NIOSH has sufficient 

information in ORAUT-OTIB-0006, ORAUT-OTIB-0079, and ORAUT-TKBS-0038-3 to support the 

ability to bound occupational medical doses for the class under evaluation. 

7.3.4.2 Methods for Bounding Ambient Environmental External Doses 

From 1990 to 1995, relatively-insensitive LiF chips were used in dosimeters; therefore, the baseline 

environmental external dose during this period is assigned based on the minimum dosimeter 

sensitivity of 10 mrem/quarter or 40 mrem/yr. This minimum sensitivity baseline results in a higher 

annual dose than subtraction of offsite background dose from onsite environmental dosimeter results. 

The baseline external occupational environmental doses for 1975 to 1989 are estimated by subtracting 

the average annual offsite background dose from the maximum annual onsite dose at De Soto. No 

data are available for the period from 1965 to 1974; however, many of the same radiological 

operations continued at De Soto Avenue during this time. The baseline dose for De Soto Avenue is 

10 mrem/yr with facility-specific dose for De Soto Avenue, Building 001, elevated to 20 mrem/yr 

(ORAUT-TKBS-0038-4). 

7.3.5 External Dose Reconstruction Feasibility Conclusion

In its previous SEC-00168 class designations (NIOSH, 2010), NIOSH has found that it has access to 

sufficient employee monitoring and workplace monitoring data to bound potential external exposures 

for employees at the De Soto Avenue Facility for January 1, 1959 through December 31, 1964. This 

current evaluation has found no evidence to the contrary for the period from January 1, 1965 through 

December 31, 1995. NIOSH has established that it has access to sufficient information to either: (1) 

estimate the maximum external radiation dose for every type of cancer for which radiation doses are 

reconstructed that could have been incurred under plausible circumstances by any member of the 

class; or (2) estimate the external radiation doses to members of the class more precisely than a 

maximum dose estimate.
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NIOSH has determined that it is feasible to reconstruct occupational medical dose for De Soto Avenue 

workers for the period from January 1, 1965 through December 31, 1995 using information and 

methods in Dose Reconstruction from Occupationally Related Diagnostic X-Ray Procedures

(ORAUT-OTIB-0006) and the Area IV site profile documents (ORAUT-TKBS-0038-1, -2, -3, -4, -5, 

-6). 

7.4 Evaluation of Petition Basis for SEC-00246

The following subsections evaluate the assertions made on behalf of petition SEC-00246 for the De 

Soto Avenue facility. 

7.4.1 Infeasibility of SEC-00234 Area IV Applies to SEC-00246 De Soto

Issue: On August 2, 2016 NIOSH initiated SEC-00234 (SSFL Area IV, 1965-1988) based on the 

inability to reconstruct dose for americium and thorium with sufficient accuracy. NIOSH stated that it 

decided not to initiate an SEC class for De Soto Facility for the same time period because De Soto 

Facility "did not work with" americium or thorium. The De Soto Facility routinely used and handled 

americium, thorium and its associated progeny, for which NIOSH determined cannot reconstruct 

radiation dose with sufficient accuracy at SSFL Area IV. 

Response: The available documentation of De Soto operations has been reviewed. There is no 

indication that the De Soto Facility performed work with americium. The document review found the 

facility held a State of California Department of Public Health Radioactive Material License 

(0015-59) allowing for up to 10 Ci of Am-241 in any form for the purpose of fabrication of sealed 

sources and transfer to authorized recipients (License, 1978); however, there are no reports of such 

source fabrication work activities in the documentation. Common commercial items can contain 

radioactive materials such as americium (e.g., smoke detectors, self-illuminating bulbs in safety 

equipment, and radiographic equipment). A significant element of the SEC-00234 finding was the 

lack of well-defined source-term information for americium or thorium produced during reactor 

operation over time. No such condition existed at De Soto, which had discrete sources of 

radionuclides. Much of the source-term information for De Soto is available through site records. 

SSFL established and maintained a centralized radiological records program. The health physics 

records containing source term and process information, including types and quantities of specific 

radionuclides and sources present, their chemical and physical form, and the types and frequency of 

operations (including controls) in which these sources were used are available to NIOSH. 

There are records of storage of materials potentially containing americium and thorium in the De Soto 

Avenue Facility vault. The storage of americium or thorium does not present an internal exposure 

hazard. The facility maintained a program to survey incoming radiological material storage packages 

prior to putting them in storage and maintained documentation of these processes, as exhibited by the 

incident report A-0200, cited in the petition and described below in Section 7.4.2 (Rowles, 1989). 

This program was intended to assure that there was no contamination on the packaging that could 

present an internal exposure hazard through inhalation or ingestion. 

The inability to reconstruct dose at Area IV is due to a lack of ability to quantify the source term in 

concert with limitations of dosimetry/monitoring methods. The conditions at De Soto are sufficiently 

different from Area IV, in that americium was not produced at De Soto by irradiation or activation 

within reactors or accelerators nor used in the production of sources. There is much clearer 
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understanding of americium use at De Soto (i.e., as sealed sources in commercial products or 

equipment). 

NIOSH has also researched documentation regarding thorium-machining work and fuel fabrication 

involving thorium at De Soto. All documentation of the dosimetry data and monitoring done for 

thorium work has been compiled for assessment of impact on the feasibility of dose reconstruction for 

De Soto workers. The quality of the data, including source term, exposure-scenario information, 

dosimetry, and air monitoring results is sufficient to perform dose reconstruction. The documentation 

also includes identifying information for personnel involved in the thorium campaigns. 

7.4.2 SRE, SNAP, and TRUMP-S 

Issue: Participated in the fabrication, examination, reprocessing, and storage of spent nuclear fuel 

including uranium-thorium (U-Th) Fuel associated with the Sodium Reactor Experiment (SRE), 

fabrication and analysis of Systems for Nuclear Auxiliary Power (SNAP) fuel, and transuranic 

materials containing americium (Am-241) under the Transuranic Management Pyropartitioning [sic]

(TRUMP-S) program.

Response: The slightly-enriched uranium metal fuel elements for the SRE were assembled in the 

Engineering Test Building (Bldg. 4003) at Area IV. The fuel was comprised of stainless-steel-clad 

rods with sodium bonding in the annulus between the fuel and the cladding. There are no indications 

in the documentation that De Soto provided support for the fuel-element assembly operations. The 

reactor’s operational period was from 1957-1964, thus fuel fabrication for the SRE would have 

occurred during the existing SEC and would not impact the period under evaluation in this report. 

The spent fuel was examined in shielded facilities at Area IV. Logbook citations (Logbook, 1964-

1965) were reviewed by an HP for indications of any De Soto work locations associated with 

fabrication or other processing of americium or thorium; none were found to indicate such exposure 

potential. 

As described in Section 5.2.1.1, the Transuranic Management by Pyropartitioning-Separation 

(TRUMP-S) program used research amounts of plutonium, neptunium, and americium radioisotopes 

associated with the disposal of spent nuclear fuel (Rucker, 2009). Originally, tests were to be 

performed in the Hot Lab at SSFL, but the work was transferred to the University of Missouri. The 

incident report cited in the petition, A-0200, pertains to a delay in performing the required radiological 

survey of a radioactive material package (Rowles, 1989). According to the internal letter, the 

shipment (received May 18, 1989) was stored in the radioactive material cabinet. Due to a 

notification failure, the package was not surveyed within three hours, or within 18 hours if received 

after normal working hours. This resulted in a NRC non-compliance. Though originally reported as a 

“lost shipment,” control of the package was never lost; the security seal was intact with no evidence of 

loss of integrity of the DOT type B container. The shipment contained 5g of plutonium and 75 g of 

depleted uranium. When surveyed, Radiation and Nuclear Safety (R&NS) staff determined that there 

was no contamination on the outside of the container (Rowles, 1989). 

The research conducted by NIOSH does not support the assertions concerning De Soto related to the 

fabrication, examination, reprocessing, and storage of spent nuclear fuel, including uranium-thorium 

(U-Th) fuel associated with the Sodium Reactor Experiment (SRE), fabrication and analysis of 

Systems for Nuclear Auxiliary Power (SNAP) fuel, and transuranic materials containing americium 

(Am-241) under the Transuranic Management Pyropartitioning (TRUMP-S) program. The available 

documentation of De Soto operations has been reviewed and does not indicate the De Soto Facility 
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performed work with americium. The document review found that the facility held a State of 

California Department of Public Health Radioactive Material License (0015-59) allowing for up to 10 

Ci of Am-241 in any form for the purpose of fabrication of sealed sources and transfer to authorized 

recipients (License, 1978); however, no reports of such source fabrication have been located. (See 

Section 7.4.5 below for a discussion of SNAP.) 

7.4.3 EPA Listed Americium and Thorium as ROCs for De Soto

Issue: The U.S. Environmental Protection Agency (EPA) listed americium, thorium and associated 

progeny as "Radionuclides of Concern" at over 60 SSFL Area IV locations during the Area IV 

Historical Site Assessment and Radiological Characterization Study. The majority of the locations 

were excluded from the SSFL Site Profile. Many were directly involved in processes and operations 

that required the participation of De Soto Facility. (Form B supporting documents, “Basis for the 

Class”).

Response: Although the Area IV Historical Site Assessment (HAS) is silent on the De Soto Avenue 

Facility and does not confirm this statement, the HSA volumes and the U.S. EPA Radiological 

Characterization Study were reviewed by NIOSH for supporting information concerning De Soto 

operations being involved with Area IV operations that could contribute to an exposure scenario 

involving americium or thorium (EPA Characterization, 2012). Although the EPA Radiological 

Characterization Study does include americium and thorium in the analytes as radionuclides of 

concern, the background threshold value and radionuclide selection rationale are reported separately. 

The EPA background study list of radionuclides of concern was initially based on the Hanford Site as 

a model and modified based on several criteria, including that the radionuclide was or could have been 

used or produced at SSFL. U.S. EPA proposed a default suite of radionuclides for soil analyses, 

including radionuclides detected by gamma spectrometry (Sr-90 [plus yttrium-90] and isotopes of 

uranium, thorium, americium, curium, and plutonium). Thus, the inclusion of these radionuclides by 

the EPA were not site-specific. Am-243 was included as a site-specific isotope where accelerators 

were used (EPA, 2012). Review of raw environmental data indicates isotopic analysis of stack and 

ambient air began in 1988. Americium and thorium were analytes, but results did not exceed 2.3 E-15 

for americium and 3.0 E-15 for thorium. 
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7.4.4 Incidents

Issue: The petitioner provided items from the Boeing Incident Report Database and states that they 

document the use of americium, thorium, and associated progeny at the De Soto Facility well into the 

site remediation period.

Response: The incident descriptions describe storage of materials potentially containing americium 

and thorium in the De Soto Avenue Facility vault, contamination incidents, and sealed-source 

incidents (administrative control violations - including TRUMP-S delivery). NIOSH researched the 

incident dataset listings with special attention to indications of work with thorium or americium at De 

Soto. All listings were reviewed and incidents of procedural violation were found; however, no 

indications of americium or thorium potential exposure situations were found other than the 

previously-identified work with thorium material. Dose reconstruction for that previously-identified 

thorium work is addressed in Section 7.2.1. 

7.4.5 SNAP

Issue: The De Soto Avenue Facility maintained a dedicated area for fabricating fuel associated with 

the Systems for the Nuclear Auxiliary Propulsion (SNAP) program at Buildings 001 and 004. Based 

on the characteristics of Americium-241 (Am-241), its relationship to plutonium, its use in 

conjunction with beryllium, its presence in relation to SNAP operations at the De Soto Facility should 

be closely examined. All SSFL Area IV locations affiliated with SNAP operations are sites where 

americium and thorium were identified as "Radionuclides of Concern" by EPA. 

Response: The SNAP reactors were operated at Area IV. Fabrication of SNAP reactor core fuel 

elements consisting of zirconium and highly-enriched uranium occurred at De Soto with the exception 

of extrusion. Fabrication operations were performed in the SNAP limited area located in Building 

001. Extrusion was performed in an isolated room at Torrance Brass Foundry, Inc. Radiography of 

certain components and elements was performed in Room 1471, Building 001. Analytical work was 

performed in Building 004. The fuel freshly fabricated at De Soto would not have contained fission 

products or transuranics (TRU); the post-testing or “spent” fuel assemblies would contain unused 

fissionable material, TRU, and fission products. Disassembly, testing, and analysis work for the 

SNAP reactor fuel assemblies was performed at Area IV, as detailed below.

The SNAP5

5 Even numbers in the reactor naming system designated compact nuclear reactors, as opposed to odd numbers that were 

used for the radioisotope thermoelectric generators (RTGs).

reactors were built to specifications for space satellite applications, so Atomics 

International (AI) chose an epithermal reactor design over a fast reactor in an attempt to limit the 

weight of the critical mass in order to limit launch costs. The SNAP-8 Experimental Reactor (S8ER) 

and SNAP-8 Developmental Reactor (S8DR) were designed and operated by AI under contract with 

NASA, and both used the same highly-enriched uranium-zirconium hydride fuel with Hastelloy N 

cladding as the SNAP 2 and SNAP-10A reactors. The SNAP-8 design included primary and 

secondary NaK loops to transfer heat to the Mercury-Rankine power conversion system. The 

SNAP-8ER was a 600 kWt reactor that was tested from May 1963 to April 1965. Testing was 

performed in a dry He atmosphere at the Nuclear Development Field Lab (Area IV) (SNAP Reactor 

Overview, PDF p. 43). 

 
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The SNAP-8DR was a prototype flight system with a power rating of 1 MWt. It was tested from 

January 1969 through December 1969 at Area IV. Cracked fuel cladding was found post-test of both 

systems. The SNAP-10A was a 43 kWt, space-qualified, Zr-H nuclear reactor, built as a research 

project for the Air Force, and launched into earth orbit on April 3, 1965. It used the same 

fuel/cladding materials as the S8ER and S8DR (SNAP Reactor Overview, 1984, PDF pp. 66-89). The 

SNAP 10A program was formally ended on June 30, 1966. All of these SNAP program reactors used 

enriched uranium fuel, the fabrication of which would not expose De Soto workers to radioactive 

americium or thorium. 

The S8ER and S8DR components were tested and their cores were inspected post-testing at the Area 

IV Hot Lab facility. Fission products resulting from the S8ER and S8DR testing would not be part of 

the De Soto exposure. The SNAP 10A was ground-tested with a nuclear reactor system that was 

operated in a simulated space environment for 10,000 hours without interruption. It was tested in 

Building 4019, the Area IV SNAP Flight System Critical Facility. Following completion of 

operations, the reactor was removed from the building and sent off site for disposal (ORAUT-TKBS0038-2, PDF pp. 19-21). The flight system flight test, FS-3, was launched into circular polar orbit 

from Vandenberg AFB on April 3, 1965. The reactor began operation after receiving a special coded 

command from ground command, 3.7 hours after launch. It is predicted to remain in earth orbit for 

4000 years (SNAP 10A, 1984). 

7.5 Other Potential SEC Petition Issues Identified During the Evaluation

During the SEC-00246 evaluation, some issues were identified that needed further analysis and 

resolution. The issues and their current status are identified in the subsections below. 

7.5.1 Thorium-Grinding Operation

Issue: In 1979, about 540 thorium plates containing ~200 kg of thorium were chamfered, removing an 

estimated 150 grams of thorium, using a surface grinder. The machinist was required to undergo 

urinalysis testing to monitor internal exposures to thorium. The machinist, and his supervisor for the 

job are in the electronic dose record database, but not for the year the grinding operation was 

performed. The assistant is not in the database. (A Review of ORAUT-OTIB-0080) 

Response: Section 5.2.1.2 of this document describes the internal monitoring results and other 

documentation related to this operation. As presented in Section 7.2.3.1, NIOSH has access to 

detailed information, including personnel bioassay data (including pre-work and post-work 

urinalysis), job performance data, source term information, the Health and Safety precautions, air 

sampling results, and access information that can be used to bound potential thorium exposures 

resulting from this operation.
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7.5.2 Controls for Environmental Pollution (CEP)

Issue: Controls for Environmental Pollution (CEP) was a primary bioassay vendor, providing 

urinalysis data used by the health and safety program to assess workers’ internal exposures to 

radioactive materials. Sample analysis results from CEP are considered invalid by NIOSH and are not 

used to assign dose because CEP was suspected of producing unreliable results. 

Response: The majority of the radiological work at the De Soto Avenue Facility was outside the 

timeframe of the CEP-contracted bioassay analysis work for the SSFL sites (August 1991 - June 

1993). The fuel-fabrication work in Building 001 ended by 1984. Building 004 continued 

radiological work, but at a reduced level. The analysis of dosimetry records, including De Soto 

Avenue and Area IV, found there to be no impact to dose reconstruction for the class due to the 

exclusion of the CEP bioassay results. NIOSH looked at the type of operations conducted at De Soto 

over the years - beginning with the reduction of radiological work in 1984 through the end of 

radiological work in 1995 - to determine if there were any significant changes in exposure scenarios. 

If there had been significant changes, workers might have incurred exposures that would be missed by 

not having bioassay results for the 1991-1993 time period. Any such changes to exposure scenarios

would need to be identified and assessed for impact on dose reconstruction feasibility. NIOSH 

determined there were no major work scope changes over the timeframe evaluated, and the Atomics 

International dosimetry program had sufficient data to support dose reconstruction. De Soto workers 

were under the same dosimetry program as Area IV workers; therefore, NIOSH would have access to 

the supporting WBC results. 
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7.6 Summary of Feasibility Findings for Petition SEC-00246

This report evaluates the feasibility for completing dose reconstructions for employees at the De Soto 

Avenue facility from January 1, 1965 through December 31, 1995. NIOSH found that the available 

monitoring records, process descriptions and source term data available are sufficient to complete 

dose reconstructions for the evaluated class of employees, including exposures to thorium and 

uranium. 

Table 7-1 summarizes the results of the feasibility findings at the De Soto Avenue Facility for each 

exposure source during the period from January 1, 1965 through December 31, 1995. 

Table 7-1: Summary of Feasibility Findings for SEC-00246

January 1, 1965 through December 31, 1995

Source of Exposure Reconstruction Feasible (Yes or No)

Internal1 Yes

U Yes

Th Yes

Am N/A

External Yes

Gamma Yes

Beta Yes

Neutron Yes

Occupational Medical X-ray Yes 1 Internal includes an evaluation of urinalysis (in vitro), airborne dust, and 

WBC (in vivo) data

As of May 21, 2018, a total of 255 claims have been submitted to NIOSH for individuals who worked 

at the De Soto Avenue Facility during the period under evaluation in this report. Dose reconstructions 

have been completed for 215 individuals (~84%). 
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8.0 Evaluation of Health Endangerment for Petition SEC-00246

The health endangerment determination for the class of employees covered by this evaluation report is 

governed by both EEOICPA and 42 C.F.R. § 83.13(c) (3). Under these requirements, if it is not 

feasible to estimate with sufficient accuracy radiation doses for members of the class, NIOSH must 

also determine that there is a reasonable likelihood that such radiation doses may have endangered the 

health of members of the class. Section 83.13 requires NIOSH to assume that any duration of 

unprotected exposure may have endangered the health of members of a class when it has been 

established that the class may have been exposed to radiation during a discrete incident likely to have 

involved levels of exposure similarly high to those occurring during nuclear criticality incidents. If 

the occurrence of such an exceptionally high-level exposure has not been established, then NIOSH is 

required to specify that health was endangered for those employees who were employed for a number 

of work days aggregating at least 250 work days within the parameters established for the class or in 

combination with work days within the parameters established for one or more other classes of 

employees in the SEC. 

NIOSH’s evaluation determined that it is feasible to estimate radiation dose for members of the 

NIOSH-evaluated class with sufficient accuracy based on the sum of information available from 

available resources. Therefore, a health endangerment determination is not required.

9.0 Class Conclusion for Petition SEC-00246

Based on its full research of the class under evaluation, NIOSH found no part of said class for which it 

cannot estimate radiation doses with sufficient accuracy. This class includes all employees of the 

Department of Energy, its predecessor agencies, and their contractors and subcontractors who worked 

at the De Soto Avenue Facility in Los Angeles County, California, from January 1, 1965 through 

December 31, 1995. 

NIOSH has carefully reviewed all material sent in by the petitioner, including the specific assertions 

stated in the petition, and has responded herein (see Section 7.4). NIOSH has also reviewed available 

technical resources and many other references, including the SRDB, for information relevant to 

SEC-00246. In addition, NIOSH reviewed its NOCTS dose reconstruction database to identify

EEOICPA-related dose reconstructions that might provide information relevant to the petition 

evaluation. 

These actions are based on existing, approved NIOSH processes used in dose reconstruction for 

claims under EEOICPA. NIOSH’s guiding principle in conducting these dose reconstructions is to 

ensure that the assumptions used are fair, consistent, and well-grounded in the best available science. 

Simultaneously, uncertainties in the science and data must be handled to the advantage, rather than to 

the detriment, of the petitioners. When adequate personal dose monitoring information is not 

available, or is very limited, NIOSH may use the highest reasonably possible radiation dose, based on 

reliable science, documented experience, and relevant data to determine the feasibility of 

reconstructing the dose of an SEC petition class. NIOSH contends that it has complied with these 

standards of performance in determining the feasibility or infeasibility of reconstructing radiation dose 

for the class under evaluation.
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10.0 References

42 C.F.R. pt. 81, Guidelines for Determining the Probability of Causation Under the Energy 

Employees Occupational Illness Compensation Program Act of 2000; Final Rule, Federal 

Register/Vol. 67, No. 85/Thursday, p. 22,296; May 2, 2002; SRDB Ref ID: 19391 

42 C.F.R. pt. 82, Methods for Radiation Dose Reconstruction Under the Energy Employees 

Occupational Illness Compensation Program Act of 2000; Final Rule; May 2, 2002; SRDB Ref ID: 

19392 

42 C.F.R. pt. 83, Procedures for Designating Classes of Employees as Members of the Special 

Exposure Cohort Under the Energy Employees Occupational Illness Compensation Program Act of 

2000; Final Rule; May 28, 2004; SRDB Ref ID: 22001 

Activity Report, 1993, Activity Report for Radiation Protection and Health Physics Services, Week 

Ending 9/3/93, Rockwell International; September 7, 1993; SRDB Ref ID: 166450, PDF p. 53 

Annual Review, 1975, Annual Review of Radiological Controls – 1975, Rockwell International; 

Release Date: July 2, 1979; SRDB Ref ID: 19137 

Annual Review, 1976, Annual Review of Radiological Controls – 1976, Rockwell International; 

Release Date: April 28, 1980; SRDB Ref ID: 19136 

Annual Review, 1977, Annual Review of Radiological Controls – 1977, Rockwell International; 

Release Date: May 27, 1980; SRDB Ref ID: 19135 

Annual Review, 1978, Annual Review of Radiological Controls – 1978, Rockwell International; 

Release Date: August 6, 1980; SRDB Ref ID: 19134 

Annual Review, 1979, Annual Review of Radiological Controls – 1979, Rockwell International; 

Release Date: September 15, 1980; SRDB Ref ID: 19133 

Annual Review, 1980, Annual Review of Radiological Control – 1980, Rockwell International; 

Release Date: October 12, 1983; SRDB Ref ID: 19132 

Annual Review, 1981, Annual Review of Radiological Controls – 1981, Rockwell International; 

Release Date: May 29, 1984; SRDB Ref ID: 19131 

Annual Review, 1982, Annual Review of Radiological Controls – 1982, Rockwell International; 

Release Date: January 29, 1985; SRDB Ref ID: 19130 

Annual Review, 1983, Annual Review of Radiological Controls – 1983, Rockwell International; 

Release Date: February 12, 1986; SRDB Ref ID: 19129 

Annual Review, 1984, Annual Review of Radiological Controls – 1984, Rockwell International; 

Release Date: March 18, 1986; SRDB Ref ID: 19128

Annual Review, 1985, Annual Review of Radiological Controls – 1985, Rockwell International; 

Release Date: July 11, 1986; SRDB Ref ID: 19142 
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Annual Review, 1986, Annual Review of Radiological Controls – 1986, Rockwell International; 

Release Date: July 5, 1988; SRDB Ref ID: 19141 

Annual Review, 1987, Annual Review of Radiological Controls – 1987, Rockwell International; 

Release Date: July 28, 1988; SRDB Ref ID: 19140 

Annual Review, 1988, Annual Review of Radiological Controls – 1988, Rockwell International; 

Release Date: May 12, 1989; SRDB Ref ID: 19139 

Authorization, May1970, Authorization for Use of Radioactive Materials or Radiation Producing 

Devices, Authorization No. 13, Rockwell International Isotopes Committee; May 8, 1970; SRDB Ref 

ID: 170465 

Authorization, Jun1970, Authorization for Use of Radioactive Materials or Radiation Producing 

Devices, Authorization No. 21, Rockwell International Isotopes Committee; June 12, 1970; SRDB 

Ref ID: 170466 

Begley, 1979, Change in the Thorium Grinding Operation Use Authorization 120, Rockwell 

International internal letter to R. J. Tuttle; March 8, 1979; SRDB Ref ID: 170500, PDF p. 3 

DCAS-PR-004, Internal Procedures for the Evaluation of Special Exposure Cohort Petitions, Rev. 1; 

National Institute for Occupational Safety and Health (NIOSH); Cincinnati, Ohio; April 15, 2011; 

SRDB Ref ID: 94768 

De Soto Notes, 2018, Missing In Vivo, Whole-Body Count Scans, handwritten notes; received March 

30, 2018; DSA Ref ID 128857

De Soto Petition, 2017, Special Exposure Cohort Petition (Form B) for De Soto Facility, with 

attachments; received December 13, 2017; DSA Ref ID: 128711

De Soto Petitioner Response, 2018, Petitioner Response & Clarifications to Summary of Telephone 

Conversation and Agreements: SEC-00246 De Soto Facility 1965-1995; [name redacted], CORE 

Advocacy for Nuclear & Aerospace Workers; received February 12, 2018; DSA Ref ID: 128791

De Soto Site, undated, Appendix D. [SSFL] Site Facilities and Waste Management Facilities, author 

unknown; Section D-7 briefly discusses De Soto; date unknown; SRDB Ref ID: 76350, PDF p. 6 

De Soto Survey, 1985, Radiation Survey for Release for Unrestricted Use of De Soto Facility, Second 

Floor, Building 104, Rockwell International; October 23, 1985; SRDB Ref ID: 163075, PDF p. 5 

De Soto Visitor Logs, 2018, Information about Visitor Logs in the De Soto Facility Log Book, 

submitted as an email to NIOSH staff; received February 27, 2018; DSA Ref ID: 128837 

Environmental Report, 1998, Site Environmental Report for Calendar Year 1998: DOE Operations at 

Rocketdyne Propulsion & Power, RD-99-115, Boeing Company, Rocketdyne Propulsion & Power; 

September 22, 1999; SRDB Ref ID: 19126 
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EPA, 2012, Final Field Sampling Plan for Soil Sampling: Area IV Radiological Study; Santa Susana 

Field Laboratory; Ventura County, California, U.S. Environmental Protection Agency Region 9; 

prepared by HGL (HydroGeoLogic, Inc.); Contract EP-S7-05-05, Task Order 0038; March 5, 2012; 

SRDB Ref ID: 158004, PDF p. 61 

EPA Characterization, 2012, Santa Susana Field Laboratory: EPA Radiological Characterization 

Study Results, U.S. Environmental Protection Agency, Region 9; November 2012; SRDB Ref ID: 

157577. The entire study can be accessed at: 

https://www.etec.energy.gov/Char_Cleanup/EPA_Soil_Char.php

ETEC, 1991, An Environmental, Health, and Safety Self-Assessment of the Energy Technology 

Engineering Center, Volume 2, Exhibits; Energy Technology Engineering Center; March 18, 1991; 

SRDB Ref ID: 90258, PDF p. 5 

GIF, 2003, Appendix B: Radiological Operations and Cleanup at the De Soto Facility, Rocketdyne 

Propulsion & Power, The Boeing Company; main document unidentified; June 12, 2003; SRDB Ref 

ID: 19145, PDF p. 4 

Grinding Log, 1979, Daily Log for Thorium Grinding Operation, F. E. Begley (Rockwell 

International); February-March 1979; SRDB Ref ID: 19105, PDF pp. 14-17 

Grinding Safety, 1979, Health and Safety Documents Related to the 1979 Thorium Grinding 

Operations; various names and dates in March 1979; SRDB Ref ID: 170500, PDF pp. 4-23 

Harris, 1970, Transit Capsule Post-Test Examination, J. M. Harris (North American Rockwell); May 

21, 1970; SRDB Ref ID: 170466, PDF p. 33 

Health and Safety, 1979, Health and Safety Analysis Report, F. E. Begley (Rockwell International); 

March 6, 1979; SRDB Ref ID: 170500, PDF p. 9 

Helgeson, 1993, Report of In Vivo Counting for Rockwell International, Rocketdyne Division, 6633 

Canoga Avenue, Canoga Park, California 91303: Work Performed on September 30 Through 

October 1, 1993, Helgeson Scientific Services, Inc.; October 13, 1993; SRDB Ref ID: 39817 

ICRP, 1975, Report of the Task Group on Reference Man, ICRP Publication 23, International 

Commission on Radiological Protection; 1975; SRDB Ref ID: 22735

ICRP, 1994, Human Respiratory Tract Model for Radiological Protection, ICRP Publication 66, 

Annals of the ICRP, Volume 24 Nos 1-3 1994; SRDB Ref ID: 22732 

Lang, 1960, Radiological Safety at Atomics International, A Division of North American Aviation, 

Inc., AI-MEMO 5468, J. C. Lang; July 13, 1960; SRDB Ref ID: 19144, PDF pp. 12-13 

Leggett, 2005, A Respiratory Model for Uranium Aluminide Based on Occupational Data, R. W. 

Leggett, K. F. Eckerman, and J. D. Boice, Jr.; Journal of Radiological Protection, 25 (2005) 405-416; 

SRDB Ref ID: 44819 

License, 1978, California Radioactive Material License 0015-59, issued from California Department 

of Public Health to Atomics International, Division of Rockwell International; October 28, 1978; 

SRDB Ref ID: 77364
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License, 1981-1991, Amendments to California Radioactive Material License 0015-70, 

Supplementary Sheets issued from California Radiologic Health Branch to Rocketdyne Division of 

Rockwell International; various date and authors from 1981 to 1991; SRDB Ref ID: 77394 

Logbook, 1964-1965, De Soto Logbook for 1964-1965, handwritten daily notebook, De Soto Avenue 

Facility; daily log entries from 1964 and 1965 (300 pages); SRDB Ref ID: 169514 

Lupo, 1999, Confirmatory Survey of Mass Spectroscopy Laboratory, Building 104 DeSoto Facility, 

Boeing – Rocketdyne; Canoga Park, California, R. K. Lupo (California Radiologic Health Branch); 

July 30, 1999; SRDB Ref ID: 76369 

Meyer, 1970, SSC Fuel Simulant Disc Fabrication Program, June 8-12, internal letter from R. D. 

Meyer to Distribution; North American Rockwell; June 12. 1970; SRDB Ref ID: 170466, PDF p. 32 

Monitoring Report, 1989, Rocketdyne Division Environmental Monitoring and Facility Effluent 

Annual Report: De Soto and Santa Susana Field Laboratories Sites, 1989, RI/RD90-132; Rockwell 

International; 1989; SRDB Ref ID: 15974 

NIOSH, 2010, SEC Petition Evaluation Report for Petition SEC-00168, De Soto Avenue Facility; 

National Institute for Occupational Safety and Health (NIOSH); March 24, 2010; SRDB Ref ID: 

134940 

NIOSH, 2017, SEC Petition Evaluation Report for Petition SEC-00235, Area IV of the Santa Susana 

Field Laboratory; National Institute for Occupational Safety and Health (NIOSH); May 11, 2017; 

DSA Ref ID: 128043 

Nuclear Activities, 1991, Nuclear Activities at Other Than Santa Susana Field Laboratories, 

Rockwell International; information requested by R. L. Holtzer (State of California); January 16, 

1991; SRDB Ref ID: SRDB 90352, PDF pp. 4-5

ORAUT-OTIB-0006, Dose Reconstruction from Occupationally Related Diagnostic X-Ray 

Procedures, Rev. 04; Oak Ridge Associated Universities; June 20, 2011; SRDB Ref ID: 98147

ORAUT-OTIB-0019, Analysis of Coworker Bioassay Data for Internal Dose Assignment, Rev. 01; 

Oak Ridge Associated Universities; October 7, 2005; SRDB Ref ID: 19438

ORAUT-OTIB-0070, Dose Reconstruction During Residual Radioactivity Periods at Atomic 

Weapons Employer Facilities, Oak Ridge Associated Universities; March 5, 2012; SRDB Ref ID: 

108851

ORAUT-OTIB-0077; External Coworker Dosimetry Data for Area IV of the Santa Susana Field 

Laboratory, the Canoga Avenue Facility (Vanowen Building), and the De Soto Avenue Facility 

(sometimes referred to as Energy Technology Engineering Center [ETEC] or Atomics International), 

Rev. 00; Oak Ridge Associated Universities; August 3, 2009; SRDB Ref ID: 72162

ORAUT-OTIB-0079, Guidance on Assigning Occupational X-Ray Dose Under EEOICPA for X-Rays 

Administered Off Site, Rev. 02; Oak Ridge Associated Universities; June 15, 2017; SRDB Ref ID: 

166967
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ORAUT-OTIB-0080, Internal Coworker Dosimetry Data for Area IV of the Santa Susana Field 

Laboratory and the De Soto Avenue Facility, Rev. 00; Oak Ridge Associated Universities; March 14, 

2014; SRDB Ref ID: 131215

ORAUT-PROC-0095, Generating Summary Statistics for Coworker Bioassay Data, Rev. 00, Oak 

Ridge Associated Universities; effective June 5, 2006; SRDB Ref ID: 73397

ORAUT-RPRT-0053, Analysis of Stratified Coworker Datasets, Rev. 02; Oak Ridge Associated 

Universities; effective October 8, 2014; SRDB Ref ID: 136245 

ORAUT-TKBS-0038-1, Atomics International – Introduction, Rev. 01; Oak Ridge Associated 

Universities; August 30, 2006; SRDB Ref ID: 30080 

ORAUT-TKBS-0038-2, Energy Technology Engineering Center – Site Description, Rev. 00; Oak 

Ridge Associated Universities; February 2, 2006; SRDB Ref ID: 22140 

ORAUT-TKBS-0038-3, Area IV of the Santa Susana Field Laboratory, the Canoga Avenue Facility 

(Vanowen Building), the Downey Facility, and the De Soto Avenue Facility (Sometimes Referred to as 

Energy Technology Engineering Ctr [ETEC] or Atomics Int.) – Occupational Medical Dose, Rev. 02; 

Oak Ridge Associated Universities; October 31, 2008; SRDB Ref ID: 53184 

ORAUT-TKBS-0038-4, Area IV of the Santa Susana Field Laboratory, the Canoga Avenue Facility 

(Vanowen Building), the Downey Facility, and the De Soto Avenue Facility (Sometimes Referred to as 

Energy Technology Engineering Ctr [ETEC] or Atomics International) – Occupational 

Environmental Dose, Rev. 02; Oak Ridge Associated Universities; April 26, 2010; SRDB Ref ID: 

80536 

ORAUT-TKBS-0038-5, Area IV of the Santa Susana Field Laboratory, the Canoga Avenue Facility 

(Vanowen Building), the Downey Facility, and the De Soto Avenue Facility (Sometimes Referred to as 

Energy Technology Engineering Ctr [ETEC] or Atomics International) – Occupational Internal Dose, 

Rev. 01; Oak Ridge Associated Universities; April 26, 2010; SRDB Ref ID: 80541 

ORAUT-TKBS-0038-6, Area IV of the Santa Susana Field Laboratory, the Canoga Avenue Facility 

(Vanowen Building), the Downey Facility, and the De Soto Avenue Facility (Sometimes Referred to as 

Energy Technology Engineering Ctr [ETEC] or Atomics International) – Occupational External 

Dose, Rev. 02; Oak Ridge Associated Universities; April 26, 2010; SRDB Ref ID: 80538 

Personal Communication, 2017, Personal Communication with former De Soto Avenue Facility health 

and safety employee; Telephone Interview by ORAU Team and NIOSH; April 18, 2017; SRDB Ref 

ID: 166532

Personal Communication, 2018a, Personal Communication with Former De Soto Avenue Facility 

Health and Safety Employee; Telephone Interview by ORAU Team, NIOSH, and Boeing Company; 

May 1, 2018; SRDB Ref ID: 172299 

Personal Communication, 2018b, Personal Communication with Former De Soto Avenue Facility 

Health and Safety Employee; Telephone Interview by ORAU Team, NIOSH, and Boeing Company; 

May 16, 2018; SRDB Ref ID: 172300 
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Rockwell, 1994, Bioassay Analysis Results, letter concerning CEP investigation, Rocketdyne Division 

of Rockwell International; December 5, 1994; SRDB Ref ID: 166179 

Rowles, 1989, Delay in Performing Required Radiological Survey of a Radioactive Materials 

Package, internal letter from J. Rowles to R. T. Lancet; Rockwell International; July 20, 1989; SRDB 

Ref ID: 169468, PDF pp. 209-212 

Rucker, 2009, Radionuclides Related to Historical Operations at the Santa Susana Field Laboratory 

Area IV, T. L. Rucker (Science Applications International Corporation); March 2009; SRDB Ref ID: 

132139 

SNAP Reactor Overview, 1984, SNAP Reactor Overview, AFWL-TN-84-14, Air Force Weapons 

Laboratory, Air Force Systems Command; August 1984; SRDB Ref ID: 172332

SSFL Operations, 1989, Nuclear Operations at Rockwell’s Santa Susana Field Laboratory – A 

Factual Perspective, Rockwell International; December 20, 1989; SRDB Ref ID: 75029 

SSFL Site, 2005, Historical Site Assessment of Area IV Santa Susana Field Laboratory, Ventura 

County, California, Sapere Consulting, Inc. and The Boeing Company for the U.S. Department of 

Energy; May 2005; SRDB Ref ID: 20531 

Tuttle, 1979, Review of Proposal to Machine Thorium, Rockwell International internal letter to 

Rockwell Isotopes Committee; February 14, 1979; SRDB Ref ID: 19105 
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Attachment One: Data Capture Synopsis

Table A1-1: Summary of Holdings in the SRDB for De Soto Avenue Facility

Data Capture Information General Description of Documents Captured Date 

Completed

Uploaded to 

SRDB

Primary Site/Company Name: De Soto Avenue Facility 

1959-1995; DOE Remediation 1998 

Contractors: 

The Boeing Company (1996-1998)

Rockwell International (1973-1996)

North American Rockwell (1967-1973)

North American Aviation (1959-1967)

Physical Size of the Site: 

Two buildings which are Bldg-101 and Bldg-104 (later 

known as 001 and 004).

Site Population: 

Varied from year to year, but appears to have been on the 

order of 100 to 200 employees. 

NOTE: De Soto related records were previously maintained at the Area 

IV of Santa Susanna Field Laboratory and have subsequently 

transferred to the DOE Cincinnati Environmental Management 

Consolidated Business Office (EMCBC). Ultimately this collection 

will reside at the Federal Records Center (FRC) - Dayton.

The entire collection of approximately 1,400 boxes consists of De Soto 

Avenue Facility, Canoga Avenue Facility, Downey Avenue, and Area 

IV combined records.

OPEN: The DOE EMCBC is processing the collection of 1,400 boxes 

received from the Boeing Company and is aware of general types of 

information that may be relevant to the EEOICPA; as such they have 

provided and will continue to provide listings of the material contained 

within the collection for NOSH/ORAU Team review. Items uploaded 

from this collection are detailed in the "DOE Cincinnati Environmental 

Management Consolidated Business Office" (EMCBC) portion below.

OPEN See EMCBC 

(line 12) entry 

below

State Contacted: [Name redacted], California Department 

of Public Health, Radiologic Health Branch

[Name redacted], California Department of Public Health, 

Public Records Coordinator 

Amendments and other supporting documentation for radioactive 

material license 0015-19, 0015-59, 0273-59, SNM-21 and broad scope 

license 0015-70, verification survey of the De Soto Mass Spectroscopy 

Laboratory (Building 104), proposed site-wide release criteria for 

remediation of facilities, methods and procedures for radiological 

monitoring, and transfer of contaminated glove box.

12/28/2009 44

Ames Laboratory Occupational external radiation exposure history records 1962-1982. 01/28/2016 1

Cincinnati Public Library Effects of Radiation and Chemical Exposures on Cancer Mortality 

Among Rocketdyne Workers: A Review of Three Cohort Studies.

09/30/2009 1

Department of Labor / Paragon Radiological incidents. 12/27/2017 2

DOE Carlsbad Summary of the NAA-47 U-10 Mo Irradiation Program. 07/12/2010 1
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Data Capture Information General Description of Documents Captured Date 

Completed

Uploaded to 

SRDB

DOE Cincinnati Environmental Management Consolidated 

Business Office (EMCBC)

Absorbed De Soto drain line fluid/sediment analyses, air sample logs, 

ambient area radiation dosimetry data summary, annual site 

environmental report, license documentation, application for renewal of 

use authorization for 30, gamma irradiation facility, radiological survey 

data, ATR fuel fabrication area decommissioning, radiological 

incidents, criticality study for EBR-II fuel fabrication, cumulative 

personnel air sampling data, procedures and plans for Buildings 101 and 

104, De Soto criticality vault documentation, De Soto x-ray facility 

information, detailed working procedures for chemistry labs, exchange 

of radiation film badges, external dosimetry program technical basis 

document, final survey reports, termination of license SNM-21, glove 

box decontamination for low enrichment line, Landauer radiation 

dosimetry exposure reports, monthly reports, spectrometry on 

plutonium containing materials, and a Rocketdyne ALARA program 

plan.

03/27/2018 128

DOE Oakland Environmental Management Consolidated 

Business Office (EMCBC)

Onsite radiological contingency plan for Rockwell International 

operations licensed under special nuclear material license SNM-21.

12/18/2009 1

DOE Germantown Area IV (ETEC) of Santa Susana Field Laboratory, De Soto Avenue 

Facility, Canoga Avenue Facility/Vanowen Building, and Downey 

Facility (The Boeing Company) search procedures.

03/07/2011 2

DOE Legacy Management - Grand Junction Office Status of FUSRAP actions, request for allocation of U-235 as UF6, 

memorandum for decontamination and decommissioning of the surplus 

facilities at Santa Susanna Field Laboratory.

06/17/2011 4

DOE Legacy Management - Morgantown National Emission Standards for Hazardous Air Pollutants Proposed 

Standards for Radionuclides.

06/30/2010 1

DOE Legacy Management - MoundView (Fernald 

Holdings, includes Fernald Legal Database)

Advance Planning Department Monthly Progress Report for February 

1977.

03/01/2007 1

DOE Office of Scientific and Technical Information 

(OSTI)

Report on survey of irradiation facilities. 02/21/2012 2

Energy Technology Engineering Center (ETEC) Annual review of radiological controls 1975-1987, exposure summary 

for decladding of gas-tagged EBR-II fuel element, historical 

radiological activities at Building 038 (Vanowen building), recent 

reviews of Rocketdyne radiological environmental monitoring, and a 

Rocketdyne environmental monitoring annual report Santa Susana 

Field Laboratory, De Soto, and Canoga sites.

12/02/2005 24

Federal Records Center (FRC) - Kansas City PM-147 incident file 1989. 10/08/2013 1
SEC-00246 07-03-18 De Soto Avenue Facility 

61 of 66 

Data Capture Information General Description of Documents Captured Date 

Completed

Uploaded to 

SRDB

Federal Records Center (FRC) - San Bruno Appraisal report occupational medical program at Atomics International 

Canoga Park, and Santa Susana, Energy Systems Group environmental 

monitoring and facility effluent annual report, and a site development 

and facility utilization plan.

09/15/2009 9

Federal Records Center (FRC) - San Bruno / Internet -

Google

Rocketdyne Division Environmental Monitoring and Facility Effluent 

Annual Report De Soto and Santa Susana Field Laboratories Sites 1989.

03/25/2005 1

Hanford Hanford laboratories operation monthly activities report (June 1958). 01/14/2008 1

Idaho National Laboratory Radiation survey reports, smear sample data, and radiation work 

permits 1974.

04/30/2015 2

Interlibrary Loan Environmental levels of radioactivity at Atomic Energy Commission 

Installations and the twenty-fifth semiannual report of the Atomic 

Energy Commission.

3/18/2010 10

Internet - Defense Technical Information Center (DTIC) Symposium on reactor fuel cycles 1970. 11/20/2012 1

Internet - DOE Comprehensive Epidemiologic Data 

Resource (CEDR)

Mortality among radiation workers at Rocketdyne (Atomics 

International), Rocketdyne worker health study final report, and 

understanding the Rocketdyne follow-on worker health study.

08/31/2009 3

Internet - DOE Hanford Declassified Document Retrieval 

System (DDRS)

No relevant data identified. 10/18/2016 0

Internet - DOE Legacy Management Considered Sites No relevant data identified. 10/18/2016 0

Internet - DOE National Nuclear Security Administration 

(NNSA) 

No relevant data identified. 12/08/2016 0

Internet - DOE OSTI Energy Citations Environmental monitoring report and proceedings of the thorium fuel 

cycle symposium,

03/05/2012 2

Internet - DOE OSTI Information Bridge List of AEC radioisotope customers with summary of radioisotope 

shipments 1964, radiation damage study on the lithium hydride shield, 

radiation recordkeeping practices at DOE facilities, and an Argonne 

National Laboratory-West summary report 1960.

09/07/2012 7

Internet - DOE OSTI SciTech Connect Feasibility report for fabrication of SNAP fuel elements, beneficial reuse of decommissioned former nuclear facilities, report for SNAP-8 

experimental reactor facility Building 010, quarterly technical progress 

report, and nuclear safety characterization of sodium fires and fast 

reactor fission products 1975.

07/14/2016 4

Internet - Energy Employees Claimant Assistance Project 

(EECAP)

No relevant data identified. 12/08/2016 0
SEC-00246 07-03-18 De Soto Avenue Facility 

62 of 66 

Data Capture Information General Description of Documents Captured Date 

Completed

Uploaded to 

SRDB

Internet - Google Area 1 burn pit Santa Susana Field Laboratory field investigation work 

plan, Atomics International environmental monitoring and facility 

effluent annual reports, internal dosimetry technical basis document and 

procedure, confirmatory survey of gamma irradiation facility, 

construction of the Sodium Reactor Experiment, De Soto Avenue 

Facility list, decommissioning De Soto, radiation survey for release for 

unrestricted use, design and development of components for the Sodium 

Reactor Experiment (SRE), license 4-698-3 amendment 1, logbook De 

Soto 1964-1965, map of Rocketdyne propulsion and power, operational 

safety unit monthly highlights, procedures for surveys of radioactive 

shipments, radiological operations and cleanup at Area IV, report on 

atomics weapons employer facilities, Rocketdyne annual site 

environmental report, radiological controls manual, Sodium Reactor 

Experiment decommissioning environmental evaluation report, former 

worker interviews, updated mortality analysis of radiation workers at 

Rocketdyne (Atomics International), and what really happened when 

Santa Susana's nuclear reactor overheated.

03/28/2018 101

Internet - Google / SC&A Aerial radiological surveys of Rockwell International facilities. 08/27/2009 1

Internet - Health Physics Journal No relevant data identified. 12/08/2016 0

Internet - International Journal of Occupational and 

Environmental Health 

No relevant data identified. 12/08/2016 0

Internet - National Academies Press (NAP) No relevant data identified. 05/02/2018 0

Internet - National Institute for Occupational Safety and 

Health (NIOSH)

Designation of additional members of the special exposure cohort 

designating a class of employees from De Soto Avenue Facility and a 

report on residual radioactive and beryllium contamination at atomic 

weapons employer facilities.

04/17/2017 12

Internet - National Service Center for Environmental 

Publications, US Environmental Protection Agency 

(NEPIS)

No relevant data identified. 10/18/2016 0

Internet - NRC Agencywide Document Access and 

Management (ADAMS)

Medical isotope production system presentations, feasibility report 

DEM-6, "Fabrication Of 164 Enriched (10 Per Cent) Fuel Pins For The 

SRE Test Program", license SNM-21 renewal, individual occupational 

exposure, and status of the decommissioning program annual reports.

03/28/2013 10

Internet - United States Army Corps of Engineers 

(USACE)

No relevant data identified. 10/18/2016 0

Internet - Washington State University (U.S. Transuranium 

and Uranium Registries)

No relevant data identified. 11/10/2009 0

National Archives and Records Administration (NARA) - 

Seattle

Health physics log sheets 1965-1966. 12/18/2014 1
SEC-00246 07-03-18 De Soto Avenue Facility 

63 of 66 

Data Capture Information General Description of Documents Captured Date 

Completed

Uploaded to 

SRDB

National Archives and Records Administration (NARA) -

College Park

Radiological Condition Surveys of Real Property. 04/13/2010 1

National Institute for Occupational Safety and Health 

(NIOSH)

Off-site data evaluation report Santa Susana Field Laboratory, draft 

final former employee interview report, plot plan - propulsion field 

laboratory map 1956 boundary line of Area IV shown, assessment of 

pond sediments in Sodium Reactor Experiment and perimeter ponds, 

and U.S. AEC product material license 4-4292-1.

05/03/2018 37

Nuclear Regulatory Commission Public Document Room 

(NRC PDR) 

Final comprehensive evaluation report on the Atomics International De 

Soto Avenue Facility, 5-year renewal of license SNM-21, annual 

environmental monitoring report for items under license SNM-21, and a 

decommissioning De Soto radiation survey.

04/23/2018 5

ORAU Team Documented communication, eighteenth annual report radiation 

exposures for DOE and DOE contractor employees 1985, external 

coworker dosimetry data for Area IV, the Canoga Avenue Facility, and 

the De Soto Avenue Facility, and internal coworker dosimetry data for 

Area IV of the Santa Susana Field Laboratory and the De Soto Avenue 

Facility.

06/16/2017 21
SEC-00246 07-03-18 De Soto Avenue Facility 

64 of 66 

Data Capture Information General Description of Documents Captured Date 

Completed

Uploaded to 

SRDB

Santa Susana Field Laboratory (SSFL) Rocketdyne propulsion and power DOE operations annual site 

environmental reports, annual review of radiological controls, 

radiological operations and cleanup at the De Soto Facility, notes on air 

sampling, use of plutonium-beryllium neutron sources for instrument 

calibration, Atomics International effluent monitoring report special 

nuclear material license SNM-21, Energy Systems Group 

environmental monitoring and facility effluent annual reports, badge 

monitoring around x-ray cells, map of De Soto Facility, bioassay log 

and results, radiation source inventory, Atomics International 

environmental monitoring program report, State of California 

Department of Public Health radioactive material license 0015-59 and 

0015-70 amendment 39-85, renewal of license 0015-70 and voluntary 

termination of 0273-70, annual radiation exposure reports, quarterly 

review of radiation safety, wound monitoring procedure, urinalysis 

results, bioassay results performed by Atomic Corporation of America, 

bioassay log and results, medical surveillance program, airflow 

measurements in ventilation systems, plutonium wound monitoring, 

radiation survey procedure for electron beam welders, control and use 

of respirators, radiation protection plan, radiological surveys including 

air samples and contamination results, radiological survey of l-77 

reactor and appropriate radiological safety procedures for the irradiation 

of poison coated snap cladding tubes, l-77 radiological safety 

procedures applicable to the irradiation of poison coated snap cladding 

tubes, health physics status l-77 reactor, De Soto mass spectrometry 

laboratory final survey plan, and room by room decontamination of 

Building 101.

06/08/2016 119

Santa Susana Field Laboratory (SSFL) / SC&A Powder Room Building 001 documentation, notes and incident reports 

1966-1968, old external dosimetry procedures and supporting data 

1970, 1987, and 1988, Atomics International health physics bioassay 

procedures.

11/18/2009 6

SC&A / Santa Susana Field Laboratory (SSFL) Decommissioning De Soto for NRC, interview of former employees on 

Atomics International, De Soto Facility, and Santa Susana Field 

Laboratory, nuclear activities at Rocketdyne, operations with Iodine131 in rooms 423-65 and 424-15 HQ.004 for vaporization studies, 

operations with solid depleted uranium dioxide, plutonium urinalysis, 

Ra-226 sources from CANEL, radiation exposure incidents, radiation 

safety unit monthly progress report 1966, respirator issuance Santa 

Susana, review of Building 055, facility and operations capabilities and 

limitations, and a summary of radiation machines registered with the 

State of California.

06/24/2010 19
SEC-00246 07-03-18 De Soto Avenue Facility 

65 of 66 

Data Capture Information General Description of Documents Captured Date 

Completed

Uploaded to 

SRDB

Santa Susana Field Laboratory (SSFL) / Nuclear 

Regulatory Commission Public Document Room (NRC 

PDR) 

Rocketdyne annual site environmental report of Santa Susana Field 

Laboratory and De Soto sites 1994.

09/24/2009 1

Stanford Linear Accelerator Center (SLAC) Report of sealed sources 1985. 02/22/2018 1

TOTAL Not Applicable Not Applicable 588

Table A1-2: Database Searches for De Soto Avenue Facility

Database/Source Keywords Hits Selected

Defense Technical Information Center (DTIC)

COMPLETED 12/08/2016

Database search terms and Internet URL are available in the Excel file 

called “De Soto Avenue Facility Rev. 00, (83.13) 05-17-18.”

120,876 0

DOE Hanford Declassified Document Retrieval System 

(DDRS) and Public Reading Room

COMPLETED 10/18/2016

Database search terms and Internet URL are available in the Excel file 

called “De Soto Avenue Facility Rev. 00, (83.13) 05-17-18.”

0 0

DOE Legacy Management Considered Sites

COMPLETED 10/18/2016

Database search terms and Internet URL are available in the Excel file 

called “De Soto Avenue Facility Rev. 00, (83.13) 05-17-18.”

0 0

DOE National Nuclear Security Administration (NNSA) -

Nevada Site Office

COMPLETED 12/08/2016

Database search terms and Internet URL are available in the Excel file 

called “De Soto Avenue Facility Rev. 00, (83.13) 05-17-18.”

0 0

DOE OSTI SciTech Connect

COMPLETED 10/18/2016

Database search terms and Internet URL are available in the Excel file 

called “De Soto Avenue Facility Rev. 00, (83.13) 05-17-18.”

266 14

Energy Employees Claimant Assistance Project (EECAP)

COMPLETED 12/08/2016

"North American Aviation" OR Boeing OR "North American 

Rockwell" OR "Rockwell International" AND "De Soto"

0 0

Google

COMPLETED 10/26/2016

Database search terms and Internet URL are available in the Excel file 

called “De Soto Avenue Facility Rev. 00, (83.13) 05-17-18.”

1,439,329 20

Health Physics Journal

COMPLETED 12/08/2016

Database search terms and Internet URL are available in the Excel file 

called “De Soto Avenue Facility Rev. 00, (83.13) 05-17-18.”

0 0

International Journal of Occupational and Environmental 

Health 

COMPLETED 12/08/2016

Database search terms and Internet URL are available in the Excel file 

called “De Soto Avenue Facility Rev. 00, (83.13) 05-17-18.”

0 0
SEC-00246 07-03-18 De Soto Avenue Facility 

66 of 66 

Database/Source Keywords Hits Selected

National Academies Press

COMPLETED 05/02/2018

Database search terms and Internet URL are available in the Excel file 

called “De Soto Avenue Facility Rev. 00, (83.13) 05-17-18.”

27,254 0

National Service Center for Environmental Publications 

(NEPIS)

COMPLETED 10/18/2016

Database search terms and Internet URL are available in the Excel file 

called “De Soto Avenue Facility Rev. 00, (83.13) 05-17-18.”

398 0

NRC ADAMS Reading Room

COMPLETED 11/10/2009

Database search terms and Internet URL are available in the Excel file 

called “De Soto Avenue Facility Rev. 00, (83.13) 05-17-18.”

682 4

United States Army Corps of Engineers (USACE)

COMPLETED 10/18/2016

Database search terms and Internet URL are available in the Excel file 

called “De Soto Avenue Facility Rev. 00, (83.13) 05-17-18.”

0 0

U.S. Transuranium & Uranium Registries COMPLETED 

11/10/2009

Database search terms and Internet URL are available in the Excel file 

called “De Soto Avenue Facility Rev. 00, (83.13) 05-17-18.”

0 0